Yes, the Media Center Guide will show your DirecTV channels if that's what you specify. You can then program recordings on your DirecTV channels and the Media Center PC will change the DirecTV Receiver's channel at the required time and record your program.
Sony SAT-T60 120GB (v3.5b)
HR20-700, HR20-100, HR21-200 HD DVR
HR10-250 HD DVR 400GB (v6.4a)
H21-200 HD Receiver
R10 DVR 160GB (v6.4a)