I only see one hard drive.
Are you recording to your system (OS) hard drive? That could easily cause your PC to freeze.
Another thing it to make sure your Video card drivers are up to date
www.geforce.com
and make sure your PACE drivers are up to date
www.ilok.com
Have you done the Windows 7 Optimizations? Or at least most of them? I personally leave Aero ON, but you may find your setup works better with it OFF.
Make sure UAC is OFF.
Always run PT with RUN AS ADMINISTRATOR
You may want to check with your Motherboards manufactures website to see if there are any updated drivers that you may need.
SP1 for Windows 7 is approved, so you may want to update that as well.
Avid Windows 7 Optimizations Video Playlist - YouTube
Windows 7 Optimizations