If you have the Gold version there is a Windows XP/2K patch.
<A HREF="http://www.gamershell.com/news_BCommandConquerGoldBWin2.shtml" target="_new">http://www.gamershell.com/news_BCommandConquerGoldBWin2.shtml</A>
If you have the original C & C then it's a DOS game with a Windows 95 frontend. Did you enable Windows 95 compatibility in XP? (Right click on the desktop icon, go to compatibility and change it to windows 95, or so I'm told. I don't use XP)
If that doesn't work try <A HREF="http://forumz.tomshardware.com/games/modules.php?name=Forums&file=viewtopic&p=8903#8903" target="_new">this thread</A>.
<b>56K, slow and steady does not win the race on internet!</b><P ID="edit"><FONT SIZE=-1><EM>Edited by phsstpok on 10/02/03 01:51 PM.</EM></FONT></P>