Using a Windows PC See Additional Information Update, at end, for help Using a Linux PC
There is no shortage of advice on creating DOS bootable USB sticks on the Web. Here is just one way that allowed me to update my AAO's BIOS. It is offered in the hope that it will take some of the guess work out of the process for others.
Having said that, BIOS upgrading is not a beginners' sport. If you don't know how to download, virus-test, unzip, install and launch applications, then you probably shouldn't be embarking on this particular adventure until you do. What follows is not a step-by-step account of the process, but rather the highlights that lead to success, together with pointers to various bear-traps that lie in wait for the unwary.
Lastly, it should go without saying, that these instructions are offered "as is" without warranty of any kind, either expressed or implied. The entire risk of undertaking them lies with you.
What's needed:
Installing the HP USB Disk Storage Format Tool
This first step in the process is to download and install the HP formatting tool. The above link is for version 2.0.6. Version 2.1.8 is also widely available, and works just as well.
Getting DOS System Files
To be bootable, the USB stick needs an operating system. FreeDOS is an open source version of MS DOS that will do the job just fine and whose kernel is available for download under the GNU General Public License ("GNU GPL"). If you happen to have an old MS DOS system floppy to hand and an A: drive to put it in, feel free to use that.
Otherwise, unzip the RipCord Bootdisk FreeDOS Kernel Zip archive from the link above to a suitable location (e.g. C:\FreeDOS.)

Formatting the USB stick
Using the FreeDOS kernel with the HP USB Disk Storage Format Tool limits the choice of usable file system formats to FAT, which in turn determines the maximum partition size. So you'll need to use a USB stick no bigger than 2 GB. But you don't need anything like that much space for BIOS flashing purposes as FreeDOS and the BIOS flasher take up less than 2 MB.
*** BEAR-TRAP-AHEAD WARNING *** The HP USB Disk Storage Format Tool will delete all existing data on the USB stick you use. In other words, using this tool to make the USB stick bootable will destroy any information already on the device. Just so there can be no misunderstanding, unless you backup the contents of the USB stick you are about to format (to a different storage device) you will lose its contents.
So if you're happy to continue, insert your USB stick and launch the HP USB Disk Storage Format Tool
Make sure that the selected device is the one you inserted (in this case a BUFFALO ClipDrive mapped to drive Z:.) Check the Create a DOS startup disk checkbox and enter the location of the system files you're using (e.g. C:\FreeDOS, or if you're using a system floppy, A:\.)

*** BEAR-TRAP-AHEAD REPEATED WARNING *** This is your last chance to save the current contents of the USB stick.

Loading the USB stick with the AAO BIOS Update
Inflate the AAO BIOS Update download directly to your formatted USB stick.

*** 2ND BEAR-TRAP-AHEAD WARNING *** Don't be tempted to rename the flashing batch file (3114.bat) to autoexec.bat on the bootable USB stick. Oh, that way lies madness.
Flashing your AAO's BIOS (Now with added screenshots)
Stick your newly bootable USB stick into your AAO and power it up, remembering to keep a finger close to the F12 key, so you can press it as soon as you see the POST boot splashscreen.

Press F12 when prompted
The stick will probably be labeled USB HDD in the Boot Menu. Highlight it and press the ENTER key.

Highlight the USB HDD option and press the Enter/Return key
You'll then see the DOS startup "belch" and be prompted to update the date and time. Just accept the current values by pressing the ENTER key for both. That should leave you at the usual DOS C:\> command prompt. If you key in dir and press ENTER, you'll get a directory listing which will reveal that the C: drive is, in fact, the USB stick.
*** 3RD BEAR-TRAP-AHEAD WARNING *** Although the BIOS Update readme doesn't mention it, it's a good idea to backup your current BIOS, in case you need to revert to it.

Press the Enter/Return key twice then backup current BIOS
To do this, key in FLASHIT ZG5_XXXX.FD /G at the DOS command prompt and press ENTER. You can replace XXXX with the current BIOS version number, if you happen to know it. FLASHIT will report the old and new version numbers when it performs an actual update.
*** FINAL BEAR-TRAP-AHEAD WARNING *** If a computer loses power during a BIOS flash update, it can leave the BIOS chip in an unrecoverable state. Some modern (usually, high-end) computers have a fail safe feature that can revert a BIOS chip to its previous (good) state if there's a problem. However, I know of no such feature on the AAO. So, to be safe, only perform a BIOS flash update when the power adapter is connected and the battery is both present and fully charged. Here endeth the lesson.

Perform the BIOS update
To perform the BIOS update, key in 3114.bat and press ENTER, and wait for the AAO to reboot.

When the Updating Block counter reaches FFFF0000 the AAO will reboot
Presto chango. Mission accomplished. (Oh, how that phrase has been cheapened.)
If you've enjoyed this feature presentation, my name is HMRAAO, otherwise, my name is George Dubya.
.......................................................................................................................
Additional Information Update
I found a couple of useful links since preparing this guide, both originating from the forum contributor macles.
Firstly, a potentially very useful tip about a built-in AAO BIOS restore feature: Acer Aspire One BIOS Recovery and secondly some help preparing a bootable USB BIOS update stick using a Linux sytem: Acer Aspire One BIOS v3.114
Copyright © 2008 HmrQtr
All guide contents is available under the terms of the GNU Free Documentation License.
There is no shortage of advice on creating DOS bootable USB sticks on the Web. Here is just one way that allowed me to update my AAO's BIOS. It is offered in the hope that it will take some of the guess work out of the process for others.
Having said that, BIOS upgrading is not a beginners' sport. If you don't know how to download, virus-test, unzip, install and launch applications, then you probably shouldn't be embarking on this particular adventure until you do. What follows is not a step-by-step account of the process, but rather the highlights that lead to success, together with pointers to various bear-traps that lie in wait for the unwary.
Lastly, it should go without saying, that these instructions are offered "as is" without warranty of any kind, either expressed or implied. The entire risk of undertaking them lies with you.
What's needed:
- A Windows PC (with Web access and a free USB port)[/*:2ymk6x4y]
- The HP USB Disk Storage Format Tool http://www.bootdisk.com/plan30/hpflash1.zip (Although widely available, this tool is no longer hosted by HP themselves.)[/*:2ymk6x4y]
- A copy of the FreeDOS Bootdisk Kernel download http://www.fdos.org/bootdisks/autogen/kernel.zip[/*:2ymk6x4y]
- The AAO BIOS Update download ftp://ftp.work.acer-euro.com/notebook/aspire_one_110/bios/v.3114.zipftp://ftp.work.acer-euro.com/notebook/aspire_one_110/bios/v.3114.zip[/*:2ymk6x4y]
- A suitable USB stick (nothing fancy and certainly no bigger than 2 GB)[/*:2ymk6x4y]
Installing the HP USB Disk Storage Format Tool
This first step in the process is to download and install the HP formatting tool. The above link is for version 2.0.6. Version 2.1.8 is also widely available, and works just as well.
Getting DOS System Files
To be bootable, the USB stick needs an operating system. FreeDOS is an open source version of MS DOS that will do the job just fine and whose kernel is available for download under the GNU General Public License ("GNU GPL"). If you happen to have an old MS DOS system floppy to hand and an A: drive to put it in, feel free to use that.
Otherwise, unzip the RipCord Bootdisk FreeDOS Kernel Zip archive from the link above to a suitable location (e.g. C:\FreeDOS.)

Formatting the USB stick
Using the FreeDOS kernel with the HP USB Disk Storage Format Tool limits the choice of usable file system formats to FAT, which in turn determines the maximum partition size. So you'll need to use a USB stick no bigger than 2 GB. But you don't need anything like that much space for BIOS flashing purposes as FreeDOS and the BIOS flasher take up less than 2 MB.
*** BEAR-TRAP-AHEAD WARNING *** The HP USB Disk Storage Format Tool will delete all existing data on the USB stick you use. In other words, using this tool to make the USB stick bootable will destroy any information already on the device. Just so there can be no misunderstanding, unless you backup the contents of the USB stick you are about to format (to a different storage device) you will lose its contents.
So if you're happy to continue, insert your USB stick and launch the HP USB Disk Storage Format Tool
Make sure that the selected device is the one you inserted (in this case a BUFFALO ClipDrive mapped to drive Z:.) Check the Create a DOS startup disk checkbox and enter the location of the system files you're using (e.g. C:\FreeDOS, or if you're using a system floppy, A:\.)
As an alternative to FreeDOS, Jcm's post viewtopic.php?p=25017#p25017 suggests simply using the systems files on the XP PC you're using, the location of which would be, for example, C:\.jcm said:... a straightforward method of preparing a bootable USB disk/new BIOS files on a Windows XP system...

*** BEAR-TRAP-AHEAD REPEATED WARNING *** This is your last chance to save the current contents of the USB stick.

Loading the USB stick with the AAO BIOS Update
Inflate the AAO BIOS Update download directly to your formatted USB stick.

*** 2ND BEAR-TRAP-AHEAD WARNING *** Don't be tempted to rename the flashing batch file (3114.bat) to autoexec.bat on the bootable USB stick. Oh, that way lies madness.
Flashing your AAO's BIOS (Now with added screenshots)
Stick your newly bootable USB stick into your AAO and power it up, remembering to keep a finger close to the F12 key, so you can press it as soon as you see the POST boot splashscreen.

Press F12 when prompted
The stick will probably be labeled USB HDD in the Boot Menu. Highlight it and press the ENTER key.

Highlight the USB HDD option and press the Enter/Return key
You'll then see the DOS startup "belch" and be prompted to update the date and time. Just accept the current values by pressing the ENTER key for both. That should leave you at the usual DOS C:\> command prompt. If you key in dir and press ENTER, you'll get a directory listing which will reveal that the C: drive is, in fact, the USB stick.
*** 3RD BEAR-TRAP-AHEAD WARNING *** Although the BIOS Update readme doesn't mention it, it's a good idea to backup your current BIOS, in case you need to revert to it.

Press the Enter/Return key twice then backup current BIOS
To do this, key in FLASHIT ZG5_XXXX.FD /G at the DOS command prompt and press ENTER. You can replace XXXX with the current BIOS version number, if you happen to know it. FLASHIT will report the old and new version numbers when it performs an actual update.
Sid said:There is a copy of the V3109 bios available from this thread. viewtopic.php?f=11&t=984&p=7593#p7593
*** FINAL BEAR-TRAP-AHEAD WARNING *** If a computer loses power during a BIOS flash update, it can leave the BIOS chip in an unrecoverable state. Some modern (usually, high-end) computers have a fail safe feature that can revert a BIOS chip to its previous (good) state if there's a problem. However, I know of no such feature on the AAO. So, to be safe, only perform a BIOS flash update when the power adapter is connected and the battery is both present and fully charged. Here endeth the lesson.

Perform the BIOS update
To perform the BIOS update, key in 3114.bat and press ENTER, and wait for the AAO to reboot.

When the Updating Block counter reaches FFFF0000 the AAO will reboot
Presto chango. Mission accomplished. (Oh, how that phrase has been cheapened.)
If you've enjoyed this feature presentation, my name is HMRAAO, otherwise, my name is George Dubya.
.......................................................................................................................
Additional Information Update
I found a couple of useful links since preparing this guide, both originating from the forum contributor macles.
Firstly, a potentially very useful tip about a built-in AAO BIOS restore feature: Acer Aspire One BIOS Recovery and secondly some help preparing a bootable USB BIOS update stick using a Linux sytem: Acer Aspire One BIOS v3.114
Copyright © 2008 HmrQtr
All guide contents is available under the terms of the GNU Free Documentation License.