Download and run the
Windows 7 Upgrade Advisor. It should give you a better idea of what will work with Windows 7 and what won't.
My best guess is that if Vista 64 drivers are available, then Windows 7 should work as most drivers are the same for Vista and 7. What is the chipset for your motherboard? nForce 430? nForce 400??
In my particular example in which there were no SATA drivers available for a s939 motherboard: the chipset was made by ULi, which no longer is in business so that's why no drivers.
FYI... I just checked the Nvidia website and it does have Windows 7 drivers available for nForce 430/GeForce 6150