http://macles.blogspot.com/2008/08/acer-aspire-one-bios-recovery.html

 Thanks BitterTruth....I tried it but it didn't work out....

 registration key ko label cha bhaney , OS reinstall gara bandhu. I dont think there is any other options if the password is in windows level. If you are lucky , check for the hints, sometime the hints is password itself .

@default, it's not a windows password he's asking for, I can crack any windows password in 2 minutes.

@koho-koho, that was just an idea. You need to find a bios update for your model to reflash it. The link above shows the similar case like yours but for different model. Sorry I didn't mention that earlier, I thought you'd figure that out.

Your system has got some sort of password written on your firmware, and flashing bios is the only option.

If I were you, this is what I would do:-
1. Try different hard drive to see if it shows POST and at least try to boot. If it does(unknown/invalid boot drive or something like that), then your harddrive(wdc wd2500bevt-22a23 ) you got when you bought has the feature to lock itself. Can't help but you need to throw it. Or I would replace the logical board to put it in use. I konw it's too much tinkering for normal user.  You can just throw it.  and install the new harddrive with new OS.

2. Re-flash the Bios.  I would take a note of my current bios and make sure with the one I'm downloading is greater version.