Q: I can't get Macbook Pro DVD drive to read my Windows 7 upgrade disk.

I have a 15" Macbook Pro running OSX 10.6.8.  I have been trying to upgrade the OS in my VMWare Virtual Machine from XP to Windows 7.  However, when I insert the upgrade disk, it just spins for a few minutes and then tells me the disk is a blank disk.  I  tried it with the drive tied to the VM XP OS, but that did not work and got the same result.  I then tried the disk in a PC I have and it seems to work fine there.  Also, I have tried other disks in my Mac drive (e.g. DVD movies) and they seem to work as well.  I am not quite sure where the problem is.  Any ideas?