Constant driver crash when rendering

Hello,

Very new to the Unity community and this is more of a hardware/getting started issue.

Fresh install, all folders installed on the same drive. Open Unity fine, create simple terrain fine, adjusting terrain height fine. Apply simple light source fine. Here's where the issue arises. When I try to render something more complex, like Pro Water or Trees, my screen freezes, driver shuts down, and then recovers.

Pentium i7 3.66Ghz, ATI Radeon 5870, Win 7 x64

I've applied the kb976038 reg edit/hotfix. I've tried every driver they made for my video card for the last year, and it's still crashing. Even when I attempt to pick a texture, the little pop-up window scrambles and causes a crash. Double clicking on something will causes a crash.

Looking for any guidance. Thank you very much for your time!