This is just a problematic machine. It wouldn't boot up at all previously until I replaced the power supply. After doing that it went on and started the boot process. I thought that was an easy job. Then after it finishes loading the Windows 2000 progress bar, I get a window asking me to run chkdsk. At this stage, whether I run it or not, it will freeze in this screen. Then after a short while, the famous blue screen of death will come out with the following error code:

c000021a Unknown Hard Error

I tried to find this error but can't. Googling only shows that c000021a message for Windows XP and that unknown hard error has some other stop message instead of the c000021a.

Could a corrupt operating system cause this problem? Or is it a failing hard drive or motherboard?

Thanks.

1.check your cpu fans
2. clean the memory
3.use dos -scandisk/all/autofix/nosummary
4.If this is not effective ,maybe your memory is broken..

Forgot to post an update back on this issue. The problem was resolved. I think the hard drive had to be replaced in the end.