Win 7, WHS v1, Ubuntu Linux, and one old Puppy Linux Laptop that is quite the antique. All operating.
In boxes? Pretty much all of the above (from computertechs list) back to several flavors of DOS.
Here's the thing Linux isn't a windows O.S
But Linux is good if you need to take windows 7 away, and add more HHD space.
When i had Linux took away windows XP, Install Linux was so confusing.
I use Linux if a customer having a issues with windows O.S or a dead HHD.
You can pull the information.
It use your processor/ Ram/ CD Rom