STOP: C0000221 Unknown Hard Error \SystemRoot\System32\ntdll.dll

[jacksonc]

Hello,

My old custom made computer had Windows XP Pro installed on it (specs down below) and it was running just fine and then I started it up a few days later, disaster struck me.  This appeared in a blue screen: STOP: C0000221 Unknown Hard Error \SystemRoot\System32\ntdll.dll and I restarted it just in case it was a one off and it wasn't so I re-installed windows XP and it happened again when the setup restarted the computer and tried to continue.  I kept on restarting and some how it started the setup again but then came to another setup error.
I would like to know a few things:
How come it started eventually
and
Could it be the hard drive that might have a error every now and then
and
Any other recommendations

Specifications:

DRAM 632mb
40GB hard drive
Wifi
VIA motherboard
Intel Celeron 1.3GHz
CD/DVD drive

Thanks,
Jackson Cropp

[Broni]

Run hard drive diagnostics: http://www.tacktech.com/display.cfm?ttid=287
Make sure, you select tool, which is appropriate for the brand of your hard drive.
Depending on the program, it'll create bootable floppy, or bootable CD.
If downloaded file is of .iso type, use ImgBurn: http://www.imgburn.com/ to burn .iso file to a CD, and make the CD bootable.

NOTE. If your hard drive is made by Toshiba, unfortunately, you're out of luck, because Toshiba doesn't provide any diagnostic tool.