If you are using XP then there isnt a fix to be able to use Dual monitor view without the drawbacks (ie. low fps on 2nd monitor). I currently have a 25.5" samsung as my main and an old ass 19" crt as my secondary. Def not recommended but with the fundage I had available it works quite well.

I set the Nvidia control to one large horizontal span so that both monitors can somewhat match for resolutions. Like I said its def not the best or recommended way to go but saving the cost of a new monitor for a short time it works well enough.