Having trouble setting up dual monitors

[Yeeesss]

Ok so I can't get my dual monitor set up working at all. I am using an ATI Radeon x800XT as my primary video card, but I also have a PCI Voodoo 3 installed which I want to use for a second monitor. (I know my x800xt supports hooking up dual monitors to it but I also have my TV hooked up to it and it doesn't support hooking them all up at the same time). Anyways I tried using System Settings > Display and checked the use dual head option and selected my video card / monitor. Logged out and restarted X and when I logged back in, my second monitor still stays blank. The dual head option is still checked but nothing is happening with my other monitor.
Anyone got any ideas?