Windows 7. I do have a Mac in the house, they are okay but a few little things are missing that I like too much about Windows. Have always been told about Ubuntu in the past, seen it in action and it looked okay but I couldn't be bothered messing around learning it for weeks on end when I don't really use computers much in the first place.
I have Windows 7 and Snow Leopard dual-booting in this PC. I like the challenge of getting OS X to work on a PC, especially on this incompatible configuration -- currently, the only thing not working is the sleep/hibernate feature. On my laptop, it's Win7 and Jolicloud (a Linux OS for netbooks, kinda cool, and easy to install too).
I mostly use Windows for games and for stuff required for school (like, having to code in Visual Studio, etc.), but otherwise, I use OS X or Jolicloud.
Edit: I've just seen another [longer] thread similar to this. Maybe someone can merge these threads...
And you created another thread on this subject, why, again? There's already one such thread, look around a bit before you post crap like this. Seriously...
Created a 10Gb hd image , inserted win xp cdrom into cd then "booted" the virtual machine. Installed windows absolutely fine. Whenever I need windows just start virtualbox, boot the image and that's it!
I think there are 2 versions of virtualbox - the OSE version but with no usb and the "normal" version which does support USB.