That's what I done on my (former) Dell notebook, left Win 2K & XP Pro on there, and created another 35GB partition for Win 7.
Whatever you do, don't destroy your XP Partition until you're 100% satisfied that you no longer want (or need) it. Some hardware (older printers & camera software) doesn't work with Win 7, sometimes there's a workaround, sometimes not.
Canon printers in particular were a common issue when 7 was released, there were numerous threads regarding these printers not working. Thank God, for the most part those threads, in addition to the non stop (which is best?) 32 vs 64, 64 vs 32 ones, were probably making a few around here needing to step away from the computer & take a stiff drink.
Installing Windows Virtual PC w/XP Mode, most software/hardware problems are solved (except games, they run like crap on XP Mode). This was the purpose of XP Mode, to be able to run our apps w/o having to depend on a physical XP install (dual boot setup or separate PC/notebook). You have 7 Pro, so it's free to you.
Good Luck, I believe you'll like Windows 7, and the learning curve isn't bad at all. Usually the ones who has problems are those who are running much older computers (from pre-Vista era) w/no Aero graphics, some also tries to compare Windows 7 to XP, and expects them to be the same (stuck in the last decade). They're not, and if you already haven't, you'll soon see it for yourself. It's really not bad at all.
Windows 7 is the very best OS that MS has produced, you'll see in no time, along with 64 bit computing. You'll now be able to take full advantage of that quad core, 4GB RAM computer.
Best of Luck,
Cat