From Task Manager, open Resource Monitor. That's the one with green charts on the right hand side. It has different context menu than the Task Manager.
Picture (on windows 8): http://thewindowsclub.thewindowsclubco.netdna-cdn.com/wp-con...
I'm not sure if Windows 7 has it, though.
Win7 has it.
In task manager, go to the Performance tab, and then press the "Resource Monitor" button.