I upgraded to Windows 7 64 bit from Vista. If launch browser it doesn't matter if IE8, Firefox, Chrome after a period of time if I perform any activity e.g. click on a link, open a new window, enter command in command prompt the system freezes for a while before responding the cpu, memory lightly utilized while this is happening. I've run msconfig, run Avira antiVirus Premium nothing special on machine. If I don't open a browser this does not happen. I have a laptop that i've upgraded also and it does not exhibit this problem.