Most dual (or multiple) displays are meant to just expand the "surface" of your application over a larger area. I have never tried to do what you're doing so, I most certainly could be wrong in saying that I don't believe that you can run a program in one monitor while seeing your desktop in another under W2k alone. Even with dual processors because most software is not written to take advantage of them won't do it. But, as I said, I've never tried it, so I could easily be wrong.
 
On the other hand, I am a little more certain that your Voodoo Rush might not be able to handle things. The "older" PCI cards most often mentioned are Matrox, ATI, some 3dfx, and certain STB cards. (I know some STB's can because I have one that does.) A lot of these had TV out features and some slow but passable 3D processing capabilities.
 
Running dual displays with two different cards does gobble up memory resources so things can get flakey depending on what you are doing.

Yeah so far it has been great, i can watch a movie on either, the rush is a couple frames or so slower sometimes. One game I could play and see the desktop on the other monitor but could not mouse over to the desktop (2nd) monitor I'm sure because the game kept the mouse from doing so. These are both 17" monitors btw. I am going to get a better PCI video card for a 2nd display and give the rush a proper burial.

It works here with a Voodoo 5 5500 pci as secondary display (pls see sig).
I can play D3D or opengl games on first display and still keep something on the other display. It works the other way for glide (UT).
Not all detonator drivers are stable though.
27.50 seems to be the best on my setup. 28 and up are less stable and I sometimes get lock-ups when dragging a window from one screen to the other. What is weird is that some apps can be moved and other do not like at all. Generally the offending apps are small single window utilities (network monitoring, asus probe...). Big regular apps can be moved without problem (Photoshop, Sequencer...).
Me too cannot move the mouse to the other display when a game has taken ownership of it.
I do not know about Rush though.
In any case, when you have got used to dual-display, you would not want to go back
It is great to edit a UT level on one screen and get into the game on the other one.

Interesting. I tried UT that way back under 98, ran an S3 and a four meg Trident (hey, it was years ago), everything ran fine, until I wanted to game. Had to disable the second display at the time. Glad to know some things are changing.

most games tell you upfront (in the readme file that they may not work on duel displays. They go on to tell you how to make the game "work" by disabling one of the monitors while you play.