I have been using a dual monitor setup since I started using computers professionally way back when in 1991. On a Mac it was easy, you just plugged another card in connected your monitor and could choose which was going to be the startup screen and arrange them left and right by dragging and dropping in the monitors control panel. Couldn't do it on a PC until Windows 98SE.

I have two 17" monitors connected to my PC which are exactly the same tis wonderful and they are not too expensive. In fact I prefer to having to 17" monitors to one single 20" screen since I get more real-estate. The card I use is an ELSA Gladdiac Twin View 511 with two VGA ports so they are both driven by that card and I have had no problems with it under Windows 98SE. You don't have to have a dual headed card, but I wanted identical screen images. You can rearrange your monitors like you do for the Mac using Win98.

Then Animation Master done the dirty on me and my files kept corrupting - too many drivers or something more like a load of old B******S if you ask me so I rebuilt my sysyem with Win2K. ELSA have gone bust so no new drivers. The ones I had didn't work as well, you could either clone the screens or have one massive desktop and dialogue boxes kept popping up split between twon monitors. This is useable but I prefer the mac/Win98SE setup.
So I have loaded the nVidia nView drivers and it kind of gets around this problem - still quite useable but I am a fussy bastard!

I have my eyes on a new GeForce 4 Ti 220 graphics card which supports multiple monitors and goes like shit off a shovel!!! Now I have to persuade the missus to let me buy it. Hope this helps you monitor maniacs... secret is I actually have three monitors but one is shitty so I use that on my Mac...