Vista - Webcam doesn't work

I have a new Dell Inspiron 1501 with Vista. I've been trying for some time
to get the Logitech Quickcam Messenger webcam to work. The mic worked at
first but never the video. I've had a lengthy exchange with the support
staff at Logitech and everything they suggest (clean installs, updated
drivers, USB port problems) is unsuccessful, so I'm beginning to think it
might be a problem with Vista. The error message I get is "Camera is
currently in use by another application." I am definitely not running any
other applications. I tested the webcam on another computer and it worked
fine. I tested a different webcam on my computer and I encountered the same
error message.

Also, in the process of trying to fix the problem, I noticed the Plug and
Play Software Device Enumerator wasn't functioning properly so I deleted it.
I don't have the system discs with me, so is there any way to download this
driver?

Thanks for the help!