|Check your hard drive with the manufacturer's diagnostics.|
See the latter part of response 1 in this:
(thanks to Dan Penny for this link:)
Hard Drive Diagnostics Tools and Utilities
If you don't have a floppy drive, you can get a CD image diagnostic utility from most hard drive manufacturer's web sites, but obviously you would need to make a burned CD, preferably a CD-R for best compatibility, on another computer if you need to.
If the hard drive itself tests okay, any data problems found can be fixed, one way or another.
If you don't which brand of hard drive you have Seagate's SeaTools will test any brand, do the LONG test, but it can only attempt to get rid of fewer than 100 bad sectors on a Seagate or Maxtor drive ( attempting the repair will wipe the data off the whole drive). Ignore the drive has been overtemp message, if you get that, if it's not a Seagate or Maxtor drive.