I've been doing this also for a couple of years now. It is amazing what most games do to a PC. Try watching your processes, services, network connections and the traffic going over them when you boot up a PC with a recent game installed on it. That's before you even run it to play anything.
Reboot to play a game is way too much of a hassle (IMO). What I'd want is a hypervisor that could handle graphics acceleration for one virtual machine at a time. When I wanted to play I just switched virtual machine and moved the ability to accelerate graphics from my workstation virtual machine to the gaming virtual machine (similar to the way some notebooks that have an integrated and a more powerful external graphics card can switch between them during runtime).
That would be a dream come true for me (if it worked well).
I did this too but had the other disks mounted (sometimes my girlfriend wants to stream media off the PC to her PS3 while I'm playing games). I have noticed that Origin will spin up inactive disks when launching Battlefield 3 (even causing the game to crash when joining a multiplayer server when the disk spinup time is > their timeout). It's ridiculous.
If a piece of software is looking for other mountable partitions, mounting them, and reading data off of them, I would think that would be looked at as incredibly suspicious.
