Windows 7 Media Center TV Frequently Asked Questions :
http://www.hdtvtunerinfo.com/win7hdtvfaq.html
Q. Does it record shows in the standard Media Center DVR-MS format used by Vista and XP?
A. No, there is a new format is called .wtv and these files will NOT play on a XP or Vista Media Center. However the old DVR-MS files will play on Win 7 Media Center.

Q. How many and what type of tuners can I configure?
A. With Windows 7 Ultimate a max of 4 analog, 4 over-the-air digital, 4 clearQAM, and 4 cablecard tuners. With Home Premium, a maximum of 2 each.