Can you tell us when this issue began? Do you have a system restore point you can use before you started to have issues?
http://www.howtogeek.com/howto/windo...ystem-restore/
If not I would run these commands:
Open a command prompt in safe mode and type in:
chkdsk c:
hit enter and let it run
Once complete run the memory tool:
Go to the start box and type in memory diagnostics and click on "start now"
Was there any issues? If not place your Vista cd in the drive and type:
sfc /scannow
Has this has been successful? If not the only option is to format the laptop. But I still think from what you have explained that this is a failing hard drive.