Cheeze,
If everything was working - then stopped, something obviously changed. I could have been an update. It could be a virus or malware. It could be some rogue driver or software that you installed along the way.
I would first eliminate malware as a possible problem. Go to this link and follow the 5 steps here before trying anything else:
IMPORTANT - Read This Before Posting For Malware Removal Help.
If these steps detect malware - follow the instructions there to remove that malware or post to the "hijack this log" forum on this site.
If your PC tests clean - try running the DirectX Diagnostics as follows:
click Start and type dxdiag in the Start Search box. Your DirectX version is listed under the System tab. The Display tab shows graphics RAM and other data on your video subsystem.
Check your game's support websites to verify Vista compatibility.
- John