I apologize for the double post.
Okay, I noticed that my CD-RW/DVD-ROM was refusing to read some CDs, including Doom, Windows XP install, Mechwarriro 4, and driver CDs. I thought perhaps the problem was this, so I replaced it with an I/O Magic DVD-+R/W 12x. I then proceded to re-install Windows XP.
However, I now get a new error for Doom (both before and after re-install). When I try to re-install, a window with the Install icon appears with the message "1158."
I cant find anything helpful on activisiosn support site... can someone help me please?