you could try this. Open WMP and click on tools/options/file types and make sure that the box that says "Music CD playback" is checkmarked. This should make WMP the default player for CD's now. If you have another version of WMP, it may or may not be the same. I just checked mine and I have WMP10.
XP, When i insert a music CD, The program Jukebox is the preference player. How can I change it to be played by Windows Media Player each time a CD is placed into D: