Running windows applications on MacOS 10.5

Hi,

I’m looking for solutions to run a third party windows application on Mac OS 10.5.

I know there’s Vmware Fusion, Terminal Services and Citrix, but are there more? And which seems to be the cheapest(don’t forget MS licenses), best and easiest to implement and support solution.
Boot camp(inside Macos 10.5) is not a solution as the users have to work in real time in this tool, boot camp requires reboot each time you switch between OS.

Situation:
a network with also 50 Macbook users need to use a custome made planning tool, only available for Microsoft platform.

Thanks for sharing your views and hopefully making my choice easier…

Jan