Here are the keyboard shortcuts for using Media Center with a keyboard. Hope it helps

Regards,
Shane.
Move up UP ARROW
Move down DOWN ARROW
Move left LEFT ARROW
Move right RIGHT ARROW
Select ENTER or SPACEBAR
Jump back one page at a time PAGE UP
Jump ahead one page at a time PAGE DOWN
Start Media Center Windows logo key+ALT+ENTER
Go back to the previous screen or backspace a single character in Search BACKSPACE
Change to a specific channel The number for the channel you want
Move up one channel EQUAL (=) or CTRL+EQUAL
Move down one channel MINUS (-) or CTRL+MINUS
My TV CTRL+SHIFT+T
My Music CTRL+M
My Videos CTRL+E
My Pictures CTRL+I
Guide CTRL+G
Record CTRL+R
Details CTRL+D
DVD Menu CTRL+SHIFT+M
Recorded TV CTRL+O
DVD Audio CTRL+SHIFT+A
DVD Subtitle CTRL+U
Pause CTRL+P
Play CTRL+SHIFT+P
Stop CTRL+SHIFT+S
Replay CTRL+B
Skip CTRL+F
Rewind CTRL+SHIFT+B
Fast Forward CTRL+SHIFT+F
Mute F8
Volume Down F9
Volume Up F10