Bulls Hit,
You only need one keyboard!
It can be done two ways... either buying a dual out video card or if you have an AGP card, buying a second PCI card (assuming your PC doesn't have a second AGP slot).
Once the second card is installed, just go into Display properties and I think it's under the Settings tab, click on the second monitor and check the box, Extend My Desktop (or something similar to that). The option has been available since Windows 98 (SE I think). You can then set up the location of the second window, ie to the right/left/top/bottome etc.
To use the second window, just drag windows in to it.. it is like having a big desktop. In Sonar, if you right (or left.. at work and can't remember which button) click on a windows top-left and select Enable Floating. Now you can drag it outside of the Sonar screen.
Hope this helps,
Porter