By computers I assume you mean actual workstations.
I have the following in the house:
* A Gateway ec1433u laptop that dual boots Windows 7 x64 and Arch Linux x86_64;
* A custom built desktop that runs Ubuntu 10.10 x86_64 (also known as mum's computer);
* A custom built HTPC that runs OpenSUSE 11.3. It serves as entertainment in the den;
* My main workstation (Intel Q6600, 6GB DDR2 800, Nvidia GTX 285, 3x 750GB hard disks, M-Audio Delta 1010LT, 2x Apple 23" displays, 2x Genelec 8020A monitors w/ a 7050B woofer, Mackie 1202-VLZ mixer, M-Audio * Axiom 61 MIDI interface) has only Windows 7 x64 on it;
* An old HP (circa 2001) with MINIX on it currently;
* An old custom built desktop that runs eComStation 2. It's used as a music server and for web browsing
* A dead Compaq Presario desktop that ran Ubuntu (mainboard and processor clapped out, it was mum's older computer);
* A working Amiga 2000HD (it even has the video toaster software and equipment);
* A dead Apple Powerbook 5300 (it turns on, but it doesn't post, and the scent of burning solder fills the air around it)
I should note that the last five are, for the most part, useless to me and I am trying to sell them (or at least the working components) off. Don't fret, I'm not a hoarder!
I live for posts of this variety.