Main machine at home Windows 7 64 bit from a SSD drive
Main machine at work, Windows XP 32 bit, extremely SLOW and bloated.
Notebook, Windows 7 64 bit (i love it on the laptop, but I barely use the laptop)
I also have Vista and XP in the main machine at home (multiboot), but Vista I need to re-install it, and I have been lazy.
Also at work I do spend quite a lot of time on a Ubuntu 9.10 server