At the least you will need to do a repair install of Windows, You will need the Restore CD for the Dell computer or a Windows CD with a CD key. You can download system drivers from Dell if you have to do a complete install. Here is a tutorial
on how to do a repair install.
Edit: In the off chance you have to re-activate windows make sure you know what your Dell licensing key is for windows.
Edited by Sneakycyber, 15 January 2008 - 06:23 PM.