I think macdrive is designed to read removable mac formatted disks placed in the drives of PCs. VMWare makes it a very different problem. The PC in there doesn't even know it's trapped inside a mac, and doesn't know about the mac drive outside it's little sandbox. One of the key features of running a VM is that it is completely isolated from the hardware it's running on by the emulation software. People use this feature to test security and virus scanning software. They infect a new VM, test the software, then throw out the VM, with no risk of it getting back to the host system.
I do believe though that the VMWare sofware has a relatively easy way to "see" the mac drive. The software sets up a network between the windows virtual machine and the mac and the mac shares it's drive over this network. It's been a while since I used VMWare though, I could be wrong.