I'm married to Windows for certain software I can't do without, but my new mistress is Ubuntu.
What I'd suggest for that, and any other versions for that matter, is to do a trial running OS from a 4GB USB drive and download it onto that using the "persistence" option that will save any changes you make to the interface, FireFox, etc. My machine, specs below, is running great on the Desktop 10.04 LTS running off a thumb drive. I ran it on a 2GB drive but it's a little tight. (One of these days I might go to dual boot, but no hurry.)
The Show Me How instructions for using "PenDrive" to install on a flash drive are at the Ubuntu site and they are first rate - see the USB Stick directions below.
http://www.ubuntu.com/desktop/get-ubuntu/download
A few things about running from a pendrive, might not apply to installing on the HDD:
1) I had real problems running the Ubuntu 10.10 "Netbook Remix" on my machine, much slower than 10.04 Desktop.
2) the HDD has to be "mounted" for access to all the data on it. I was very confused when my DropBox on the HDD kept delinking but learned it's because of the time lag between booting and mounting: answer is to disable apps that require HDD access from system startup,
3) FireFox runs pretty well on the default installation, but much better if you use about:config tweaks to disable disk cache and run it in RAM, and change the pipelining settings. Speed tweaks for FF are easily googled.
4) the wi-fi interface is a little weird for bringing up different screens - I think the 10.10 version is improved in that regard - but once my WPA2 passphrase was registered, it's logging on automatically no prob.
5) there is a system password login app called KeyRing that seemed to pop up from nowhere at first, but eventually it gave up and shut up.