Others here will correct me if I am wrong, but Virtual PC, (I don't know VMWare), is "installed" into an OS. While you may be able to install the software onto a different hard drive, the OS drive still has significant files and settings as well as registry entries needed for the OS to run it.
That said, it seems that "VirtualBox" attempts to do something of what you require and you may want to read more about that here; http://maketecheasier.com/install-virtualbox-in-usb/2010/01/02
But lets see what others say.
I have a few classes at a college that require me to have two virtual machines running at once, however the removable drives that they use are really old and frequently crash which does me no good when I have to reload the OS then Virtual PC program, then the two Virtual Servers.
My question is I have a 1TB Seagate Portable HD, I want to find a way to Load either VMware Player/Workstation or Virtual PC on to the portable hard drive, and be able to take it to another computer at the college that also has VMware Player/Workstation or Virtual PC to do my labs. Will this work, and please don't respond with just a yes or no answer, I need to know how to do it if and why it will or will not work.
My system: Windows 7 x64 with VMware Player/Workstation with the following virtual machines loaded: Windows XP x86, Windows Server 2008 & 2008 Core.
College System: Windows XP x86 with Virtual PC x86 with the following virtual machines loaded: Windows server 2008 (x2) and 2008 server Core.