Powerdesk has been keyed to detect a Matrox product in order to be used now. This didn't use to be the case. It's been like that now for at least a year now though. I have a spare Th2G Digital just sitting around so I plugged it in to bypass the hardware detection issues I have for Eyefinity and Surround use.
If that's the case, it hasn't stopped me from using it. I recently switched from AMD to Nvidia and I find PowerDesk far more functional than Hydravision ever was - I can actually do a simple double-click maximize without having the window span the entire monitor array. As for getting it to work (Win7), I just downloaded the program off their website, installed it, then setup my borders like I did with Hydravision. Didn't have to go through a wizard or anything like that.