Unkown error after installation and restart

Hi, I have a 2.8 Ghz, P4 processor with 768 (512 + 256) MB ram and an Asus p5rd1-vm motherboard with a 128 MB ATI-Radeon Graphics Card. I have been running Windows XP for years. I have decided to upgrade to Windows 7 finally after reading all the reviews. I managed to get windows 7 installed but after i rebooted, "unknown error" appeared on screen. Any ideas why? I have not upgraded my BIOS (bcoz I don't know how to safely do so for my hard disk). Is this a reason? Please Help

Yes, Installation was complete, then it asked me to restart and then this error message appeared. Some one was saying it might be bcoz I have an outdated motherboard, but I've read a ton of reviews online in which systems with much lower configs have easily installed 7.

I didn't try Safe mode... but I did reboot it again...same problem

Thats an older machine and 7 really doesn't run well with less than a gig of RAM ....but it should boot up
mis-matched RAM doesnt help you might just pull the smaller stick out and try to boot with just the 512
I know it sounds odd but that's at least consistent the system needs to be ale to access all sectors at the same speed .... anyway it may be an issue

how did u do the install ??? you need to go to customize install and delete and reformat the disc and then install to the freshly formatted clean disc this is known as a clean install

Bios should not be a factor not enough RAM or hard disk problems might present and issue for the installation

It was a clean install (Brand new hard disk). Will try what you said and see

Umm.. I have to change my battery, the thing is everytime I disconnect my system from the power supply and then restart it after, I have to update date/time, maybe that's the reason.