The BEST way for running VM's (Please note here I'm not talking about XP MODE HERE) is to use something like VMWARE server (FREE).
You can then have the VM's start automatically in the Background at boot (and shutdown).
The nice thing about this is that a USER can log directly on to a VM WITHOUT having to have an account on the HOST machine. (Needs an account on the VM of course). -- This is a great way of say running a Webserver - on the Virtual machine.
What's even better if your VM's are SEVERS as well then your users can log directly on to the application (for example ORACLE / SAP (etc etc) without even needing an account on the VM either.
If there's enough people who are interested I'll try and make a tutorial on how to set this up.