Ever since the Windows 10 upgrade was announced as free I have tried off and on to install it in a copy of my Windows 7 Virtual Machine (that I run on my Mac). At least I can get on with work and life while trying major OS upgrades that way. Unfortunately it’s not worked until finally I got somewhere today.
1. Switch your hard drives and DVD drive to IDE not SCSI.
2. Don’t worry if you missed the Windows 10 free upgrade deadline. Use your Windows 7/8 product key or the ‘assistive technologies’ upgrade.
For some reason VMware Fusion that I’m running defaults new Hard Drives to SCSI, though you can change the (emulated) connection type to IDE or SATA. It appears that Windows 10 doesn’t really like SCSI. Whenever I tried to install – either through ISO or running an upgrade assistant I got an error or else it would let me choose a keyboard layout then only give troubleshooting options and insist on shutting down or restarting the PC, without actually installing windows. Then it would revert to Windows 7, sometimes reporting error 0xc1900101 – 0x20017.
This turns out to be driver-related and probably was the SCSI issue.