Emachines problem

I have a emachines that i just restored it using the included restore cd a couple months ago. I have Microsoft office and macromedia studio on it, the only programs. for some reason though it will freeze up and if i press ctrl alt del it will bring up the task mananger, and everything is running so i click exit out of it and everythin works. also it just started within the past week to reboot at random. i already turned off the auto restart.