I also have Windows XP Professional (32-bit), Windows Server 2003 Enterprise Edition (32-bit), and Windows Vista Business (32-bit) running in Windows Virtual PC.
Well if we are going to count servers than add Redhat Enterprise Linux 5.x and CentOS 5.x to the list. And I suppose I use Windows 2008 Server as well depending how you look at it.
Windows 7. I remember when I first downgraded (sic) to Windows Vista, updated back Windows XP Pro SP3 a day later but now after using windows 7, you can never go back ;D.
the first os i use is - Windows 3.1 - Windows 3.11 - Windows 98SE - Windows Me - Windows 2k - Mandriva Linux - Windows XP x32 - Ubuntu 10 - Windows 7 x64
windows vista is skipped when using it feel like using junk windows. full with problem not support auto ip renewal when win7 born i think this is the best
Main PC: Windows 7 retail/boxed x64 | FreeBSD x64 | Arch/OpenSUSE/Ubuntu (whatever I have to. Usually just install Ubuntu in a Virtual machine since I get a headache from that crappy os.) Laptop: Windows 7 retail/boxed x86 Tenshi (home-server): Windows XP x86 (formerly Arch Linux/FreeBSD)
On my laptop I have Windows 7 Ultimate 64-bit, on my gaming rig I have the same thing, and on this other computer in my room I have a dual boot of the the 32-bit and Ubuntu 10.04, but I never really use that one.