It seems that the Webcam driver of your Dell is managed by Microsoft, try to update it with this version but be aware that it's outdated (2006-06-21) and may not work.
The integrated options of Windows Update or from
Device Manager >
Imaging Devices >
Integrated Webcam >
Update Controller >
Update from Windows Update should give you the newest driver available.
Some search with the hardware driver related me to drivers.adwit and it seems that it isn't a standalone driver and depends of some other like
usbvideo.inf that are managed too by Microsoft.
If this don't work, try updating EHCI and the BIOS and check that you have no options in BIOS and in keyboard that don't allow you to use the camera.
If nothing works, install Dell System Software, it should search all the drivers for your computer, if something is missing it will install.