Microsoft changed things up again. Back in the day (Windows 2000, 2003, XP, etc.) you could easily open Windows Task Manager using Ctrl + Alt + Del, then pressing T. Now in Windows 7 and Windows Vista you can still use Ctrl + Alt + Del which displays a screen whith options like Lock this Computer, Switch User, Log Off, Change Password, and Start Task Manager. However, pressing T does nothing, and in fact, no keyboard shortcuts work on this screen to choose one of the items from the list - even tab and arrow keys don't let you pick from the list. You have to use your mouse pointer. Stupid, stupid, STUPID! Way to go Microsoft!
So to launch Task Manager in Windows 7 and Vista you would have to go through this double step process of pressing Ctrl + Alt + Del, then reaching over to your mouse and clicking on Start Task Manager. I can understand Microsoft trying to make things easier for new users and for the masses. But for heaven's sake please leave old keyboard shortcuts in place for those of us who have been using Windows for a while.
Enough ranting and raving. Although this has probably been the case all along (this old dog had to learn a new trick), you can use Ctrl + Shift + Esc to open Task Manager directly and bypass the hassle and frustration introduced by MS with Vista.