Yes, with hacked drivers if you want to game, and you won't need hacked drivers if you're running the nvidia card for cuda and not for anything graphical.
It will work, but the Catalyst Control Center, and by extension, the Vision Engine Control Center are a load of old horse balls. You have a good chance of problems, just warning you.
I've got the opposite situation going on, 5870 running two monitors (including the primary on which games are played) and an 8800GT running a third monitor. Simply installed the 8800GT, booted up, let default drivers take care of the 8800GT since it's not running any games. In the reverse situation it should be very much the same, no need for CCC at all. I'm not exactly sure how work is distributed between the two, to be honest. I can run windowed games spanning multiple monitors, even monitors controlled by different cards. The only problem has been when I was poking through CCC options and wondered what would happen if I tried including the Nvidia controlled card in an Eyefinity display group. I was promptly greeted with a BSOD.
