I’ve seen the following problem on random Windows 7 computers when trying to upgrade to Windows 10 version 1607.
Basically, using System Center Configuration Manager Current Branch to upgrade your Windows 7 X64 SP1 computers to Windows 10 version 1607, the upgrade fails or appears to hang for a very long time. This doesn’t occur on all computers, but is random in appearance.
When the problem does occur, you need to troubleshoot with CMTrace. By examining the setupact.log available in C:\$WINDOWS.~BT\Sources\Panther on a computer exhibiting the problem, you’ll notice that Windows Setup hangs indefinitely on the following line:
Install the following Knowledge Base article from Microsoft KB2952664 on your Windows 7 clients prior to attempting the upgrade to Windows 10 version 1607, this will allow the upgrade process to complete successfully.