It's been a while but I think media center has a volume slider on it, doesn't it?
Windows 7 is pretty elite. Good choice SD. Do you have an Xbox 360? Completely compatible with Windows 7.
Ever use a projector with your computer? Press Windows Key+P and check that out.
Windows key + Home makes all windows minimize except the window that you're using. Gets rid of clutter.
Ever get that annoying "You do not have sufficient rights" message when running a program? Then you have to "run as administrator" ? Well, no more. Hold Ctrl and Shift when you double click the program and you automatically run it as administrator!
Tons more of elite tips, but I have to save some for the other guys.