I think you posted the same message in another forum.
The guys advice there seemed pretty good. Check the cabling
etc. Did u do that?
Did you open the case lately to change/modify/clean components?? Did you hear any noises lately from the hard disk? Can you try it in another or a friends computer?
DOES your BIOS see the hard drive?
Can you boot with a floppy disk (windows boot disk)
and do a "dir" on the C drive?
Do you have access to Partition Magic (there is a check for errors there)?
And like the other person said, what OS?
The loving are the daring!