As far as I know there are only two ways of getting your computer back to factory restore IF you have the Dell Vista DVD and the Dell Drivers DVD. If you don't have the disks, then I suggest you contact Dell ASAP and get them. The first option still may not work but worth trying. You will need to know the drive letter of your Recovery Drive. I have two hard drives so mine is J: at the moment.
Figure 3: Language Settings Screen
Figure 4: Install Now Screen
NOTE: If the Windows Vista Setup program detects any problems on the computer, you may receive the following message:
Figure 5: System Recovery Options Window
Windows found problems with your computer's startup options.If you receive this message, click No.
Do you want to apply repairs and restart your computer?
Figure 6: Windows Found Problems Window
Figure 7: Choose a Recovery Tool Window
Note: The following instructions require a Microsoft® Windows Vista™ DVD which includes the Windows Vista disk that was originally shipped with your computer or any Windows Vista DVD displaying the Windows Anytime Upgrade logo . In addition, the Recovery partition must not be damaged.
dir [this will just bring up a list of the files on the drive to make certain you are in the correct drive. There should be a folder called Tools]
In the Dell Factory Image Restore window, click Next.
Figure 2 - Factory Image Restored Window
Click Finish to restart the system.
If that method doesn't work, then the only other way is to reboot to the Dell Installation DVD and instead of hitting the Repair Your Computer, you click on Install Now and you install Vista from the beginning. You then have to put the Drivers DVD in and individually reinstall the drivers for your computer. The drivers dvd does help you to do this by detecting what devices you have and telling you which ones you have to install. But each one has to be done manually.
I have taken my computer back to XP and haven't missed Vista one little bit. I used my own copy of XP but was able to use the Dell Driver dvd to install the XP drivers.
Best of luck with this......