I am trying to reformat a Dell Inspiron 1501. When I go into Disc Management to reformat the hard drive, format is greyed out. Does anyone know how I can change this so I can reformat the complete hard drive. I have tried to just reinstall Vista and it kept stopping half way through. In the end I had the operating system on the computer three times. It is now working but I cannot get rid of the Windows Old files to delete the unwanted information. I would be grateful for a reply as I have been trying to solve this problem now for 24 hours. All help is appreciated.

You can't format a drive you have booted from. You have to boot to another drive, then you can format that drive.