It's built into windows (multiple monitor support)
I have regularly set up 6 screen for traders (two rows of three)... probably that business is dead now for me.
The trick is multiple video controllers or a fancy (read..expensive) single controller with multi-heads
Most video boards (not the on-the-motherboard ones, but the plug-ins) support 2 monitors...for 6, we add two more boards.
You can arrange their virtual positions any way you want in Windows.