There is a problem in 98 where the CD-ROM doesn't refresh within "My Computer" when you place a disc in it. I've seen this on other machines I'm sure.
Try and install another game (at least two discs long) and see if the problem reoccurs. You can also try hitting F5 while in "My Computer" which is refresh the window; if it doesn't then it's the refreshing problem.
At least if you try a 2 disc game, you'll know if it's the DD copy or your system.
