Your OS.

[Raognerrrm]

Mac OSX 10.6.7.
Because I hate Windows and I don't trust any of the various Linuxes enough to not damage my computer.
It's easy to use, has terminal, a great call centre, it (so far) runs everything I want it to, and I find it much more intuitive than anything else I've tried.
It also gives me much more control over everything.
Finally, it has some great free development tools that surpass anything that Windows has thrown at me.

 

[Zanderinfal]

Windows XP. Don't wanna change.
EVER.

Also, I do not want to buy a new comp, just upgrade to the newer graphics cards, processors, etc.

 

[kasperbbs]

Windows 7 64 bit. It runs great, never crashes and i don't have to reinstall it every 3 months because it gets slow (looking at you XP), plus it's the best operating system for gaming right now.

 

[trollnystan]

I use Win7 on my stationary computer and Xubuntu on my laptop.

Win7 'cos that's my gaming computer, and Xubuntu 'cos the laptop is old, used to have Vista (hiss!hissss!), and I always wanted to try Linux. I only use the laptop for surfing, reading, and writing anyway. Works out good =)