Actually you can, Linux is able to read (and often write) drives that have been formatted by windows. My guess is it has something to do with the fstab file, but I have little experience with this so I will wait for someone more knowledgeable to post on this one
Is the secondary drive formatted as FAT or NTFS?
Files can be easily read, but running windows programs under Linux is another thing. Playing his music should be no problem once he gets this sorted out.