Things to do:
1. Turn off your computer.
2. Turn it on, boot it and log in.
3. Open the device manager and look at the version number of the video driver. Write it down somewhere.
4. Do that over-the-top install you always do.
5. Open the device manager again and check the version number.
6. Compare it with the previous result.
Case #1: Versions are different.
Your OS is broken or you put it into sysprep mode or something like that. You can try to find the issue, but it might take a lot more time than just reinstalling the whole thing. If you want to look for the problem, check windows update first. It's notorious about overwriting drivers, maybe that's what reverts yours all the time. Make sure you don't let it do that.
Case #2: Versions are the same.
There a bug in the driver detection algorhythm of the game. Contact the publisher and report it, and ask for help.
CPU: AMD Phenom II X4 810 @ 3120MHz | RAM: Kingmax 2x2GB DDR2 800 @ 833MHz| MoBo: MSI K9A2 CF v1.0 (BIOS: 1.D)| GPU: Asus HD 6850 1024MB (DirectCu) @ 835/1135MHz | Display: L24FHD | PSU: PC Power & Cooling Silencer 750 Quad | OS: MS Windows 3.11 Pro x64