Hello marsse3, Link Removed to Windows 8 Forums,
Have you tried this driver; Link Removed
On one of my builds, I was running a HD3450 and if I'm not mistaken, I got the 1st driver through Windows Update, then installed the driver from the link I just provided, also, I don't remember if I ran it in compatibility mode, I'm pretty sure I didn't, but I do know that I used the AMD driver suite for that card in Windows 8 with no problems.
Hope this helps
Don