Yup 2K would be fine, 98 I hate with a passion and I don't know if its supported in the newest version of VPC? I don't actually know too much about VPC, as in, do you have to use the version of windows that comes with it, or is it possible to use and activate if appliccable another license (you can get, or could get before VPC was bought out, Virtual PC with FreeDOS I believe it was)...XP isn't actually too expensive these days, 2K is about the same price as Pro OEM I believe at about £95...
But for a single app, I guess 98 would be fi...no just get 2K/XP Much less pain.