A couple of weeks ago, John Doe wrote a tutorial about how to make Linux work after you've installed Windows XP, which, of course, has made your Linux primary partition inactive.
Well, let's say you try a different solution, like I did, the one found here (Recovering GRUB after reinstalling Windows section). Everything was fine and dandy, except I couldn't boot Windows after that. What was the problem? I'm a noob, so of course I didn't know. Luckly, there is #ubuntu, with some very helpful people. They helped solve the problem, so I figured I'd share the solution.