I'm glad that someone is starting to take interest in making modern drivers work on Windows Vista. Unfortunately, even NVIDIA recently stopped supporting Windows Vista as of driver version 365.19, and the new GTX 1000 series cards have no Vista drivers at all. I'm wondering if an INF mod to the Windows 7 RTM drivers would be sufficient to make the drivers work. Even if driver updates eventually put a stop to the INF modding method, at least there would be a working driver for the GTX 1000 series.
I don't have any AMD cards to test drivers, but I do have a GTX 760. I may try the latest drivers on Vista when I get a chance, and report back with results, so at least NVIDIA users would also know where Vista compatibility stands on that boat. Unfortunately, even if modern GPUs had Vista drivers, you're going to be stuck with using either Ivy Bridge or FX series processors, because Intel Haswell and later just simply won't accept Vista in any shape or form, due to a bug that causes the boot process to fail (although not every time, it happens in about 1 in 5 reboots from my testing). I'm not sure exactly what happens, but somehow, the services just don't seem to start up in the correct order, and it causes the whole boot process to fail, which throws up the "Interactive logon process initialization has failed" error message. Changing numerous BIOS settings did nothing to fix this, and installing all the latest updates also didn't fix it. Hopefully someone on here will look into this issue and find out what is exactly causing the problem, because as it stands now, Vista is pretty much unusable on Haswell because of this.