winxppro activation?

i never activated my xp pro, how do i check how many days i have left until the activation thing pops up
i've been running this version of windows for i think 1.5-2 years, the activation thing never popped up before

You don't. If it hasn't popped up by now, it never will. You have the corporate edition, meaning no activation at all. If you were running anything else, you would get the activation message regularly telling you how many days are left.