Hi and welcome to the forums. Drivers
automatically downloaded and installed off Windows update should not
be relied on.
They often are incomplete, faulty or buggy.
Always use the software provided with your hardware or the appropriate download from the manufacturers website (in the case of Microsoft Windows Update can
count as their website but for no other brands, I would still advise against relying on it).
Please can you tell us the make and model of your webcam so we can point you to an appropriate driver
download, also please feel free to use the drivers provided on the CD that came with your webcam for now there is a high likely hood that they are outdated though.
Also, to help us out on the forums please fill in your System Specs under User CP.
If you have any questions just ask.
Post back with any success.