Hey Ranald,
I recently switched to a 2 monitor display.
I tried this at first with a less powerful Graphics Card and it was a nightmare. As well as a BIG reduction in Frame Rates I also had other endless issues including lock-ups and crashes.
Then... I upgraded my Graphics Card to a ATI X800 256/256 card and tried again and got great results.
Essentially you just need to buy an adaptor that allows your second monitor to connect to one of the spare sockets on the back of the Graphics Card (there are usually 3 output sockets but 3 different connector types, so the adaptor is needed to connect the second monitor to the card).
Then I simply went into CONTROL PANEL and DISPLAY and clicked on the second monitor icon to activate the second screen.
Using the set up with FS is a little more tricky....
I have to dash just now so if you want to know more, shout up and I'll go through all of the exact steps in order to use multi-monitor with FS.
😉