I tell you what I'd try. It can f****** up your system, so do it only at your own risk.
1. Rip the built-in drivers from windows 8.
2. Download and extract 13.4 legacy.
3. Overwrite files in 13.4 with the ones ripped from the OS. Leave config and inf files intact.
4. Disable driver signature enforcement.
5. Try installing the drivers.
This *may* work in a sense that you'll have the built-in drivers and opengl as well. CCC/VECC won't work, don't even bother installing it. Note, that this is theory only, I haven't actually tried it.
CPU: AMD Phenom II X4 810 @ 3250MHz | RAM: Kingmax 2x2GB DDR2 800 @ 833MHz| MoBo: MSI K9A2 CF v1.0 (BIOS: 1.D)| GPU: Asus HD 6850 1024MB (DirectCu) @ 850/1100MHz | Display: L24FHD | PSU: PC Power & Cooling Silencer 750 Quad | OS: MS Windows 7 Pro x64
CPU: Pentium 4 Northwood S478 @ 3200MHz | RAM: 1,5GB DDR 400| MoBo: Gigabyte GA-8S661FXMP-RZ | GPU: ASUS Radeon X1650 Pro 256MB | Display: Dimarson 19" CRT | PSU: Noname 400W | OS: MS Windows XP Pro