You can try a free memory diagnostics at
www.memtest86.comHave you tried using System Restore go back to a point
before installing Google?
Is that all of the protection you have?
Download
CCleaner (without Yahoo! toolbar) and reference
this guide.
Download/install
AVG Free, update it, and scan in Safe Mode.
Although I'm not quite convinced that this is an infection, a
HijackThis log can help us see if you still have bits and pieces of the Google toolbar on your computer. You never know, getting rid of it all might help.