You can run a vm on a atom processor but it has to have at least 2 gigs of ram , you can do it on 1gig but its really laggy and doesn't respond very well.

Try using Qemu though instead of virtbox or vmware.

You can't literally shut of a P/S no but you can shut off a computer and its pretty easy on windows or *nix based distros. Also you can write malware so that it does destroy a HDD you can destory sectors or just format the whole thing.

Yeah I know it a old post but hopefully its helpful.

Always use some sort  *nix based distro for your host.
Now you could try for your host promox  http://pve.proxmox.com

which uses KVM (kernel virual machine)  which is based on Qemu so it will allow you to load any kind of OS including Windows accept for 95 because its DOS based.

then you could play and tinker with multiple OS's at the sametime and network them together and hack on them.

If you want a great OS to lean on try http://archlinux.org

My 2 cents.