I use Win7 64 bit Ultimate and havent run into any issues with CCC.
I would d/l and try using MSI Afterburner (much more robust tool).
http://event.msi.com/vga/afterburner/download.htmThere was a link on these forums regarding finding the sweet spot for your video card by adjusting core clock settings.
http://bitcointalk.org/index.php?topic=4292.0I tweaked my card settings a bit (HD6850) and am running ~210Mhash/s @ 74C stable (I also work on that computer while mining as well).