Even at home, I realized I routinely use four different machines. Try that on a damn tablet.

1) My main machine. Right now, running Windows 7. In the past, it has run everything from various KDE-based distros to off-brand Linux distros only heard of by some housecats living in rural Minnesota.

2) Our Linux server that I remote into using NX and\or putty.

3) A virtual machine running Windows XP for various work-related tasks.

4) Another Windows 7 virtual machine for testing/security.

That’s what I use just at home. And yeah, I really do use those all at the same time.