|How much has this laptop been used?|
If it's been opened and closed a lot, if Windows doesn't find the web cam at all, it's quite possible the wiring is damaged for the web cam between the base and the lid, probably where it passes through the hinge. In that case, it MIGHT work when the lid is in certain positions, and not work when it's in other positions.
The wiring can be replaced - replacing that wiring bundle is a common repair.
Have you EVER spilled liquid on this laptop?
It doesn't matter whether it was running at the time - it can be damaged even if it wasn't, because the mboard is always powered in some places when the main battery is installed.
Has this laptop EVER been dropped?
Have you re-loaded Windows from scratch from a regular Windows CD since the web cam last worked? If you have, you must load the main chipset drivers after Setup is finished, otherwise Windows will probably not find all your devices properly.
Look in Control Panel under Scanners and Cameras - do you see anything there for it?
If you don't, did you try using Control Panel - Add Hardware to see if Windows can find it, or some unknown device?
If you don't see it there, Windows Add Hardware can't find it, it's wiring is probably damaged.
If you do see it there....
Did you un-install any drivers listed in Control Panel - Add/Remove Programs for the web cam before you installed the drivers? If you didn't, do that, reboot, and try installing the drivers again.
Note that is often NOT a good idea to install drivers for something when Windows detects a device while booting, you allow it to look for drivers, then when it doesn't find any, you point it to where the driver files are. You should Cancel that if you see it, continue on to the desktop, then install the drivers using it's installation program, or follow installtion instructions - there may be a Readme or similar file in the download when it's files are extracted, or included with the download.