Try running Norton's Disk Doctor from a clean boot and do a full surface scan for bad sectors.
- Restart and press F8 just before Windows begins to load and select "Command Prompt Only".
- At the command prompt type, "ndd" (without the quotes) and press enter.
- Before starting the scan go to Options and select "Fix Errors Automatically". If you don't select this you'll have to manually ok each repair which could get very tedious/time-consuming.
Note that this operation may take several hours or overnight to complete depending on the amount of errors (if any).
Disk Doctor should be able to find and fix any bad sectors and mark them as bad so that data is no longer written to the bad areas. If there are a great many bad sectors it may be time to consider a new drive. With only a few bad sectors the drive should be ok long enough for you to backup the data before replacing the drive, at least it won't be running slow/crashing on you once it fixes any disk errors.
Good luck
JohnE.