Same

If its a dark screen what you can see then you can do one thing "on the cam window under OPTIONS check/uncheck the PREVIEW option" and check if its working.
If it says "no video capture device found" then the drivers you have installed are not fully compatible with VISTA, for this you can do one thing---
1. Remove the previously installed webcam drivers, delete the installation folder from Program Files if its still there, disconnect (unplug) the webcam, reboot the system , Scan the registry using ccleaner (freeware).
2. Install the program you use to access the web cam (eg: amcap etc).
3. Now attach the webcam (be connected to the internet), when the driver installation screen pops up click "Install automatically" it will search for the system files for the drivers or go to the windows update (this works many times) if not found.

Once done & successfully installed the webcam shall work fine now.