I don't think it's a problem with the system. I'm still using VM Lite XP Modes, because I don't trust in Windows 7. You know, I drove more than 200 complete races on the few XP Modes I have and the game has never crashed yet during a race (except freezing errors with 3 or 4 special tracks, but I fixed this already). I started a complete race on Windows 7 once, but the game crashed after about 75% of the race distance.
A screen with something like "GP4.exe has occured a problem and have to be closed. Searching for a solution for a problem." appeared and that was it, the race was over then. So never ever again I will drive a GP4 race with Windows 7! I hope you understand this decision. I already changed some settings with the XP Mode's graphics, but nothing changed.