A PC at home and a Toughbook laptop, both Linux+Win32.
On PC I have Windows Vista - arghh. Since my parents bought the computer quite soon after Vista was released, they purchased it. I am planning on switching to Windows 7 from MSDN AA, though. Linux distro here is Linux Mint, as it has a nice GUI and everything is quite user-friendly. Only had some minor issues with sound card drivers (Sound Blaster X-Fi). A shame I can't get FPC to compile anything using non-standard units.
Toughbook has WinXP - I would not even dare trying W7. XP runs quite nice, though I use it mainly for gaming. Linux distro here is Fedora, running an LXDE desktop. So far my only problem is being unable to find a working driver for the touchscreen, but other than that, I daresay everything runs like a dream.
Reasons to moving from Win to Linux? I was curious about Linux for a long time, but I only gave it a try after I got my own computer. One of the reasons was also going to university - I knew there would be some subjects regarding Unix\Linux, so I thought it could be good to check it earlier. After some adventures with different distros (I tried six or even seven), repartitioning the HDD several times, et cetera, I decided to stick to Fedora+LXDE. Now, over a year later, I use mostly Linux, mainly for being able to change literally everything in the system's runnings (not that I was lucky enough never to have it not running after some of my experiments...), it's stability and ability to be customized. Running programs with WinKey+Letter is wonderful - and addictive, to the point I created registry entries for like 20 apps in WinXP just to be able to run them via the Win+R "Run application" applet.
A funny fact to end the post - when at home, I most often use both computers. I work at the PC, with the laptop sharing it's disk via NFS. No need to worry about transfering files or whatever.