Well, I was trying one thing at a time, and GTL was still crashing. So I tried it all at once, underclocked the card, set fan to 80%, set settings to low, shadows to off and plr settings to those that Navin pointed me to. An I was able to do 12 laps at Lime Rock before stopping on my own. So it seems problem is somewhere in there, and now I'll experiment with setting to see how much more performance I can get back.
Thanks to all for the help.
I had a similar problem to this some months ago. Make sure your power setting is set to high performance in Win 7. With my PC it seemed to go into sleep / power saving mode ignoring the fact that GTL was running. Hope this helps I know how frustrating it can be.