I am not sure if this will be of use to anyone as it is an issue that appeared when Windows 7 first came out and both Logitech and MS seem to have long since washed their hands of it but I never found a working solution anywhere.
I have a Logitech QuickCam Communicate STX which I have spent the last two days trying to get to work on 7 x64, after trying several different drivers without success I finally resorted to letting the OS search for one online and to my amazement it found one.
It is showing as version 11.0.0.1213 and the camera is visible in device manager.
The old Logitech software for my camera is not compatible with 7 and the new software is not compatible with my camera, in any event they are both blocked from installing.
On my old XP PC I had a copy of
Screen Camera which I have just transferred across to the new one, it immediately picked up the camera and both sound and vision are working.
Screen Camera is not free but the point is that at least some Logitech cameras that are supposedly incompatible with 7 can be made to work on it, quite possibly with other software.
If this information is available elsewhere my apologies but I could not find it.