I was using Windows XP, then I switched to Linux Ubuntu, then I couldn't stand playing Blockland on Ubuntu so I tried switching back but it didn't work. So now I'm trying to get Win7.
Installing 7 on an XP computer probably wouldn't be the best idea. See if you can find an XP install disc.
Linux generally is not good for games. That's why you had trouble with Ubuntu.
If you are unable to reinstall XP, I recommend installing Lubuntu. While it's just as bad for games, it should be lightning quick on nearly any hardware it's compatible with.
Blockzilla incoming.
Holy stuff, you perfectly called it. And he didn't even mention it anyway. What the forget just happened here.