What OS do you have?

[LifeExpired]

Vista Ultimate 64bit.

Lewis.

[Camouflage]

Desktop PC: XP Pro SP3
Notebook: Vista Home Premium
(got vista ultimate on DVD...but too lazy to install it)

[freedom91]

Vista all the way! :)

[thefalling]

Slackware 12.2 -old desktop
Slackware 12.1 - baby laptop (asus eee)
Ubuntu 9.04 - ibm thinkpad R51
Windows XP - Visual studio bloated laptop im currently on
Windows 2k -older than old desktop
And pretty much every other conceivable OS i could get my hands on, on VMs.

[TriumpH]

win xp laptop
win xp corporate work laptop
win 7 desktop

[kuribohgx]

Windows Vista SP1 x64 bit. :D

[Tyler]

Windows XP Home
SP3

[cape88]

Forgot to post PC's:
Windows XP SP3 (I think)

[bitblaster]

Laptop - Mac OSX 10.5
Desktop 1 - Mac OSX 10.4
Desktop 2 - Windows Vista Ultimate
Desktop 3 - Ubuntu Linux
Desktop 4 - Windows Vista Ultimate
Laptop 2 - Windows XP Professional
Phone 1 - Blackberry OS
Phone 2 - Palm OS
Phone 3 (Hasn't arrived yet) - Blackberry OS
PDA 1 - Palm OS
PDA 2 - Windows Mobile 5
And my Cisco router says it runs Linux...
Also have a VPS Running Linux, Don't know if that counts.

[Furiosity]

I have XP Pro SP3 in desktop, XP Pro SP2 in Compaq Presario Laptop, and Vista SP1 in Dell Inspiron Laptop.

[allo99]

windows 7 build 7057

[Hejula]

PC1: Windows Vista Home Premium SP1
PC2: Windows Vista Home Premium SP1

LAPTOP1: Windows Vista Home Premium SP2 Beta
LAPTOP 2: Windows Vista Home Premium SP1
LAPTOP3: Windows 98 Seccond Edition SP2.1a

[Socket_Monkey]

Main : Enchanted Fedora Core + Windows XP Pro Sp3, Streamlined

[jointhegroups]

windows proffesional sp2,
Windows XP SP3

[MAXTRAXv3]

windows xp sp3 32bit, to keep the compatibility up!
only down fall is DX 10 and 11