depending on the strength of your desktop machine, you might want to use vmware... this is especially useful if you have a powerful laptop (because you can develop anywhere). I do this, and i am under the impression that a number of people here do to (i am pretty sure Don B. said he did in another thread) - i now have something better, but i used to do it on a 800Mhz Athlon with 384 ram, and a 7200 rpm drive... it worked fine.
Vmware offers a 30 day trial, but after that it will cost $300 for a regular customer and about $140 if you are in education.
