For what machine
Server #1 It has to be linux it is a 133MHz ARM board with 32meg of RAM (like hell you would get windows on that) NSLU2 is the product, very nice
Server #2 (main server) it is linux and it is up 24/7 acting as home NAS,HTTPD,FTP,SSH,... like hell I would trust windows for my server or with my Data
Desktop: Has Gentoo Linux as the OS cause well its too damb configurable and fun to work with. Why linux tho? because
1) stability
2) I want to use MY hardware for MY usage and NOT feed an inneficient OS ( I mean FFS you need 2Gig of RAM for Vista to start to become Usable and while I do have 4Gig of RAM only 100Meg of that is for the OS - Openbox FTW meaning the rest of the RAM and CPU-time can be used for gaming and simulations)
3) Customisation
4) If something goes wrong I can repair it (short of a filesystem corruption/harddisk crash). If a tiny bit of windows dies BOOM, re-install
This machine also Dual-boots to Windows-XP (more for those what-if cases and the odd couple of games that I can get working well in WINE)
Also on this machine there is 4x Virtual machine
#1 = Window2000 (I like this OS, nice and small and efficient so good for me to test windows things while still in linux)
#2 archlinux - More for a buildhost for my server #2 (which is arch )
#3 Ubuntu - more because I support a few friends and family on ubuntu so I kinda need to have it avail for those few specific ubuntu things
#4 Fedora - like above but for the work machines I support.
VM's are good for nice sandboxed testbeds
Laptop #1: eeePC - it boots in 5sec to the SLiM login screen for linux. Too nice
Laptop #2: Dualboot XP and Ubuntu (mainly XP for wife)