When it freezes try Ctrl Shift Escape (all three at once)
This brings up Tak Manager
See what's eating the machine
Applications, Networking, Processes.
Do some housekeeping
Remove Spyware (Spybot Search & Destroy) free
Tidy Registry (Piriform's CCleaner) free
Defrag disk (System utility)
Good luck...
Peccavi, October 2009