There are at least two ways to do it.
1st without any extra software, simply open both programs, right click on taskbar and click "Show windows side by side", or whatever it's called in XP (I'm on Vista right now).
Secondly, plenty of free programs, which will do it for you: http://www.google.co...p...gram&aqi=g1
Finally, I definitely recommend second monitor. I've been using dual screen for quite a while and I can't leave without it. If money is at stake, you can get used LCD monitor, say 19", out of Craigslist for 50 bucks.