I don't know what causes that. Recently switched to Win7 from XP & I can't understand why my PC starts lagging so bad after a few hours of use & forces me to reboot. I got 2 gb of RAM (which is enough). I do the usual stuff.. browse web, watch movies & play games mostly. But after a few hours of use the memory usage goes above 1.5-1.7 gb & touches 2 gb. Even if i close all the programs I was working on. Why I didn't experience this on XP ?