At the last place we actually did PC game development, the QA department was huge.
We had 20 PC's each with different motherboards. Each of them were fitted with a hard disk docking cradle and a set of hard disks. Each hard disk had a different operating system on it (or version of OS's, so we might have three version of XP per machine as well as windows 2000, and several versions of Linux)
Then we would have a bunch of graphics cards.
Before release a game would have to pass QA on ALL combinations
This is why I hate PC games development, give me a platform where I know what hardware I have to run on please.
The only solution I have is make sure the end user has up to date drivers for all hardware, get him to send you a list of hardware and drivers.
Then either go to their site and have a look, or buy an equivalent setup. There is no @magic bullet@