I might not have been clear on one point. These VMs are frozen. If they got infected, it would clear when the VM is shut down. Each VHD is read-only, so not even a possibility of me committing a change to the VHD unless I really meant to do so. If I installed MSE - then "The VM cannot easily be frozen." Is what I meant to convey.
The fact that they are frozen is why IT allowed an AV exception; otherwise, I would have to install a rather bloated corporate Symantec AV tool.
These VMs run minimized on my office workstation for short periods of time. I think that splitting the CPU cores makes the host more responsive; I could be wrong. The IT dept does not support these VMs. This is just my setup to do my work faster - using the stuff that I can get my hands on and things that I've learned on my own. So it is I that is in the stone ages :-)
My apologies if I've taken this thread too far from the OP's world - but obviously, I think that there is room for discussion about AV tools inside frozen VMs. If the OP decides to run a VM without AV protection, then the OP should also isolate that VM from the host's hard drive and freeze the VM.