Easy guys, 
 
I am havig problems with my laptop. 
 
Every now and then, it freezes, as in, I can move the mouse, but can't exit anything, use Ctrl Alt Delete etc etc. On my main account, 10-15mins 
On the guest account, 25-30 mins. 
 
I seems to freeze quicker when firefox is open. I'm not a n00b to computers, but it's really baffled me. I have checked for malware with malwarbytes, and spyware etc with AVG9. 
 
I am using an IBM Thinkpad T-60, 3 gigs of ram, 1.84ghz cpu. Ati Mobility Readon x1300... 
 
What could you computer wizz kids reccomend to do? 
 
Thanks, Jack.