How many Linux Distros have you got installed

How many Linux Distros have you got installed on one Hard Drive?

Debian GNU/Linux unstable branch
FreeBSD 6.2
Debin GNU/Hurd K14

But I'm only familiar with Linux. The other two, I only installed recently. And what? K14 is now oldish. I'm still taking baby steps in learning to use it. Soon gotta upgrade to its latest release.

As for FreeBSD, I use it as a backup system. I know for sure that I'll mess up the other two so badly one day. So I put this FreeBSD as a backup system just to keep the PC running in that time. But not conversant with this as well. Many commands seem familiar, so looks a bit easier than GNU/Hurd.