This is probably a really stupid way to do things, but I have never had much success with VMing...
I use an SSD in addition to the standard HDD on my computer. The SSD has Mint 13 w/Xfce (and some othe WMs/DEs), and is the heart of my stable, amazing, Supergirl system that runs anything I want, including a viewer to an online environment that I have been unable to make run on any other Linux distro. The HDD generally has an Arch build I am working on, and a rotation of other distros (which is very slow now, really Mint and Arch have risen to the top for me, as great complements). I don't do anything risky to the SSD/Mint, but try most anything on the HDD.
This is where it really gets stupid, I think, but I don't know a better way. I loaded Mint on the SSD with the HDD unhooked, so it only has a bootloader for that disk, and for Mint. When I add a new distro to the HDD, I unhook the SSD, as I have lost access to my Mint before trying to add stuff the HDD with the SSD installed. So, the HDD also only has bootloader for the HDD, and hopefully the OSes on it. (Though, I have lost access to the first OS when I added the second many time, too. I think you can go in and edit the GRUB to get it back, but usually I just start over). Most of the time, I have both disks hooked up, and when I want to switch OSes, I just reboot and interrupt the BIOS boot and select the drive I want, and go about my merry way.
And while I am sure I don't hold the record for completely trashing OSes, I have definitely taken several to the point that I had to just reinstall. Probably someone with more knowledge and experience could have fixed them, but at least I learned a lot in the process. Linux is so much fun!