[fowlplay4]

The plethora of unoptimized scripts on UN would do that, you've also got some other program taking up the other 50% of your CPU.

What I could do:
1. Decrapify (It's got plenty of HP crap still on it) the PC. Google 'Decrapify'
2. Remove Mcafee or Norton (if present), Install Microsoft Security Essentials if necessary.
3. Minimize the number of Startup processes in msconfig (Windows Key + R, msconfig)

What I would really do:
1. Download a clean MSDN copy of Windows 7 Ultimate
2. Format + Reinstall with clean copy

Update your video drivers as well. Go to Nvidia's site.