Help with an the Screen of a Acer Aspire Laptop

I have a Acer 5734Z-4836 laptop (2.5 years old). In the last couple of day, I have notice if the computer sits for more the 2 mins without any activity. the screen goes black. You can tell the back lights are on (the screen doesn't go completely off), and if you touch any key on keyboard, the monitor will come back on. Its like the monitor goes to sleep. I have not touched any of the power settings for months, I have reset them to never turn the screen off (for the battery and AC settings) in Windows 7, and the screen still goes to "sleep" after just 60 to 90 seconds of inactivity. I have AVG basic virus program, and it has ran and found nothing . The only thing that has changed is about 3 weeks ago I replaced the A/C adapter with an generic one. I am on this Acer a lot, and this problem has just happened very recently. Does anyone have any thoughts on why the screen goes to sleep after a very short time of inactivity? Thanks,

 

Hi everyone, I bought an used Acer 5734z that freezes on Acer logo. I changed ram, cpu, power charger,......everthing. I removed cd rom, hdd, wifi and nothing happened.
Everytime it turns on, i tried to access to bios pressing F2 and itfreezes again.............I turn it on and I press Esc key and shows bios post and freezes again!!!......I decided to upgrade bios.......but when it starts the bios flashing process (obviously pressing fn+Esc before plug the power charger and turn it on) the notebook turns off and I cant turn on if i dont unplug the power charger.
Suggestions? I tried using the latest bios, the first one, all software includded, only the .fd file.......is all the same......it turns off!!!