I have Chessmaster Grandmaster Edition which has only one disk, and Chessmaster 9000 which comes with 2 disks. I installed them on Windows 7 computers and they work perfectly, even with the DGT board. Sorry, I can't answer your question definitively, but I hope it helps somewhat. Cheers, John C.
ChessMaster XI Grandmaster Ed

In the last month, I've purchased Chessmaster 9000, 10th Edition, and Grandmaster. Chessmaster 9000 came with two discs, and they are both CD Roms. Chessmaster 10th and Grandmaster editions both came with one disc a piece, and they are both DVD Roms. I would assume that if you only have the one disc, then that is all you need.
Be sure to download the latest patch.
http://forums.ubi.com/showthread.php/341421-Chessmaster-Grandmaster-Edition-Downloads

Well spotted! I just checked and my double disk set consists of CD's, whereas the single disk is a DVD. This tends to support what you say kkbell. Good obs. Cheers, John C.

I have a Chessmaster 10 for PC that came with 3 CD discs, so Ubisoft must have transitioned from CDs to DVDs during the Chessmaster 10 era.
I bought a used ChessMaster XI disc set for my pc. It only came with one disc. The box appears to be made to hold more than one disc and the instructions refer to inserting disc 1 to install. That would infer that there are more discs.
Can anybody tell me how many discs are supposed to be in the set? If this proves that I've been shortchanged then any suggestions on where I can purchase the set or download on line?
Thanks in advance, I am,
Bummed in Oregon