in-place Upgrade to XP Pro from XP Home

At some point in doing an in-place upgrade of XP Home to XP Pro from an XP
Pro with SP2 disk (Systems Windows Client: Business License) the install
program ceases to recognize the Upgrade Disk in the CD Drive. When prompted
to enter the drive where the disk resides, the program does not "see" the
disk in the CD drive. The install continues but Windows Management
Instrumentation information appears to be corrupted which means that I can't
make the necessary adjustments in advanced network connection properties to
transfer files to a new Vista machine (my ultimate objective).