os whore
An individual who has no preference in operating system, and has numerous operating systems running on their personal computer(s) may be considered an os whore.
OS Whore: My media center PC has 5 hard drives, it boots Windows Vista, Windows Media Center 2005, Mac OS X, Ubuntu, Fedora, and Gentoo.
Innocent Bystander: You're a total OS whore.
Innocent Bystander: You're a total OS whore.