Not that I doubted you but well, I'm stubborn. I went to the Microsoft site for Virtual PC and they have a Google group set up to answer questions for the software. I found a thread
here that talks about using Virtual PC 7.0.1 and ACT! 2005. It appears that it can be done but be prepared for things to run rather slowly unless you can add a fair bit of memory to the Macs.
Hope this helps.