I'm no great expert on this, but I'll do what I can since no-one has answered so far.
1. Go into the BIOS Setup and check that the HDD is being seen by the BIOS and correctly identified
Also make sure that all your drives are set to "Auto" detect.
2. Would be a good idea to run the HDD manufacturers diagnostic utility to test th HDD to see if it's healthy.
3. Which Windows version is installed?
4. Use fdisk to look at the partitioning. See if it looks OK and whether the 1st Primary Partition [the C: partition with Windows on it] is SET AS ACTIVE.
Set it active if it isn't.
5. That should do for now, but the next step would be to restore the MBR..
AND/OR...
6. Make an NT/2000/XP boot floppy and use that to attempt to load Windows
Check out
http://www.dewassoc.com/kbase/hard_drives/master_boot_record.htm