|Make sure your hard drive is not in the process of failing !|
Check your hard drive with the manufacturer's diagnostics.
See the latter part of response 1 in this:
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.
Seagate's Seatools will test (almost) any brand of hard drive.
Do the long test.
The bootable Dos versions of SeaTools can be used even if Windows is not working properly.
If the hard drive itself tests okay, any data problems found can be fixed, one way or another.
If the hard drive itself DOES NOT test okay, you need to REPLACE it.
"Will just have to do a complete recovery to sort it all out."
Doing that WILL delete the personal data that you have added that is on the same partition Windows was installed on.
If you want to copy personal data you don't want to lose that is on the same partition Windows was installed on to elsewhere, you do that BEFORE you do the Recovery procedure.
E.g. If Windows is not working properly, you can boot the computer from something such as a Linux CD, or the Ultimate Boot CD, that can read all the data on your hard drive
Doing a Repair installation of Windows WILL NOT delete the personal data that is on the same partition Windows was installed on.
See response 10:
Scroll down to:
"- If that doesn't help, you can try running a Repair installation of Windows"
Also - SATA RAID (and IDE RAID) - see the first part of response 10
Also - if you have the bios Setop set to have the SATA drive controllers in SATA or AHCI (or SATA RAID) mode
Installing XP and SATA drive controllers, SATA drives; the SATA drive controller bios settings.
See response 2: