Thanks! Then im afraid you will have to re-install windows....
(Dell Windows Vista Recovery from Factory image)
1) Start the computer.
2) As the computer starts, press the F8 key until the Advanced Boot Options menu appears on the screen.
3) Press the (Down Arrow) to select Repair Your Computer on the Advanced Boot Options menu, and then press Enter.
4) Specify the language settings that you want, and then click Next.
5) Log in as a user who has administrative credentials, and then click OK.
6) Click Dell Factory Image Restore.
7) In the Dell Factory Image Restore window, click Next.
8) Click to select the check box for Yes, reformat hard drive and restore system software to factory condition.
9) Click Next. The computer is restored to the default factory configuration.
10) When the restore operation is completed, click Finish to restart the computer.
If this is not working, you will need the Dell Vista Re-Installation DVD. If you do not have it, call dell or order it online as its FREE and FREE shipping by FedEx.
NOTE: You will need your Dell Disc to re-install windows if the first option does not work.
1) Turn on the computer
2) Start tapping/pressing F12 to get Boot Menu Options
3) Insert Dell Vista Disc
4) Select DVD/CD-ROM and press enter
5) Press any key to start the installation
BEST OF LUCK!