OK, so what O/S? What type of PC (sony, dell)? How long have you had it? Does it hang doing anything, or just certain things? How much RAM does the machine have? Have you tried to uninstall the last program you have installed? When was the last time you defragged your harddrive? is it waiting on applying updates? Do you have antivirus installed? What kind? How much free space do you have on your harddrive?
Let us know!