Any driver released by Logitech needs to be signed by Microsoft.
You might have installed another manufacturer's driver, and had to dismiss a "Driver Not Signed" or "Digital Signature not Found" warning when the driver is enumerated.
Logitech doesn't do this, all our drivers are signed by Microsoft's Windows Hardware Quality Labs (aka WHQL).
Under Vista 64-bit, the OS itself will not allow any non-signed drivers to even load! The only way around this "driver lock" is to load Vista 64 into a special diagnostic mode (called Test Mode). Additionally, to be Vista certified, Microsoft says all drivers need to run under both Vista 32 and Vista 64.
Now, to get this signature from Microsoft, drivers and hardware (note the bold highlight) must pass a stringent set of tests given by WHQL. The actual testing process takes hours per camera, and includes such things as putting the system on standby and waking it up many many times, connecting and reconnecting the device many many times, checking for malformed USB packets, testing the microphone, and lots of other techie nonsense.
Last year, in preparation for Vista, Microsoft updated these tests (now termed DTM).
The old hardware immediate ran into issues with the new tests, and did not pass. The exact same hardware passed the earlier test fine. But you can't use the earlier test with Vista, you must use the new test.
Engineers spent time tweaking drivers so that some old cameras where able to pass the tests and could get the signatures. For other cameras, an exemption had to filed and reviewed by WHQL.
Unfortunately Microsoft has told all vendors that this exemption process will close completely after one year, so time is running out for these older devices."
"Given all this, adding Vista support for older cameras gets caught in a vicious Catch 22. The camera and drivers need to pass tests to be signed. Due to test changes, the old hardware can no longer pass the test, so an exemption has to be filed and reviewed.
For some cameras, we got through this relatively painlessly. For other cameras, this is much more difficult."