Windows 7, everything vista was supposed to be but with the hardware requirements of xp and the very nice improvements of vista.
At 50$ for preorder, and free upgrades to 7 if you run vista. It's a good deal. If you run windows, get 7. If you run xp, it's defunct, old, showing its age, and you'll be left out in the cold real soon with it.
Get the cheap newest version of windows that'll run on old hardware while you still can.
Other than that. I don't give a rats ass. Microsoft is still no longer an innovator, despite improvements their quite stagnant, and windows 7 only really exists because of netbooks.
The only reason people still go for windows is because it's familiar. Who cares that all of the notifications, dialogues, and prompts that treat the user like a retard because the user base can't get with the times because they run as admins all the time.
Windows was only truly good with win2k and xp. After that they got into the mood of we can sell our customers **** and they'll bite it up.
So......when the many of you who have microsoft update/windows update set to automatically update the system....how many times does windows still tell you to "click here" to install updates regardless. How many times does windows tell you that you need to either restart or remind you later to restart and apply the updates because microsoft happily doesn't include a "don't remind me anymore" button. How many times does windows remind you that you may have no antispyware/malware/antivirus software on your computer despite having it or not everytime you boot up?
**** windows, i'm not a retard, it's really one hell of a bull**** platform these days.