It shouldn't do that on XP, unless you have another program causing the problem. If you have an antivirus or similar program running it could also interfere with it, or you might have a bad disc. If you can't sort it, and you have a good internet connection, you can also just register your serial and download the whole game:
1) Get
Stardock Central (our download manager, used to get patches or even the entire game should you not have your discs handy to install from).
2) Install it and log in with the same account you made for the forum.
3) Go to the Tools menu in SDC, and choose Register Products.
4) Pick Games on the left in the Register Products window, then find GalCiv2 in the Product pull-down menu. Enter your email address (same as forum account, again) and serial number, then click Register.
5) Back at the main screen of SDC, pick Games on the left. You should see GalCiv2 under a Purchased Products heading on the right side. Select it and click the Update button that appears.
6) Click the + next to GalCiv2 and get the additional modules as well.
That should do the trick. If you encounter an error message while trying to register the serial in (4), please contact
[email protected].