Weeks/months ago we had this series of events on our Dell desktop computer:

STOP:C000021a{Fatal System Error}
The windows logon system process terminated unexpectedly with a status of Oxc000000(Ox00000000). The system has been shut down.

I think we then turned it off and on and got the following:

Loading PBR for descriptor 2...Done.
A disk read error occured.
Press CTRL+ALT+DEL to restart

When you Press CTRL+ALT+DEL to restart the same message appears

Loading PBR for descriptor 2...Done.
A disk read error occured.
Press CTRL+ALT+DEL to restart

This is a Dell Dimension 3000 that we bought in 2004.

Thank you in advance for your input!