Greetings from good old Germany to this famous site

Regarding M:TW I recently encountered a problem in the game: I installed XP over my old W2K and just set the link to the exe file without reinstalling the game. Now when I play a new campaign (doesn't matter if English, French or Spanish, always Early Age) I have the problem that I cannot produce anything better than archers. Otherwise every unit works correctly, but even if you have a bowyers guild or better I cannot produce Xbows or better. Bug? Or just plainly reinstall? TIA for help

Greetings