SymptomsThe upgrade to Parallels Desktop for Mac 4, 5, 6, 7 or 8 from Parallels Desktop 3 is taking too much time. It just hangs.
CauseMost of the time, this is caused by pop up window that is hiding behind the upgrade screen. Usually, it is either login screen, or Windows asking to reactivate.
ResolutionFirst, you'll need to switch to manual upgrade mode in order to continue.
Press "Ctrl+Cmd+Alt+R" buttons simultaneously and when prompted, hit "Yes" to switch.
You will see the pop up notice/message that is hiding behind the upgrade screen. Complete the action required (depending on the Windows message) and the upgrade will continue automatically.