When we upgraded our Windows 8.1 VMs to Windows 10, we had to set one cpu or the upgrade failed.  Seems like the same thing applies in the Windows 10 upgrade being offered from Microsoft to upgrade to 1511.

 

Stop the Windows 10 VM, set only one cpu, then start the VM and proceed to upgrade Windows 10.  Once it has completed the upgrade, you can set the number of cpus back to more than one.

 

If Windows 10 refuses to upgrade, you can re-install Windows 10 and keep all your files and settings by using the Windows 10 iso and run an in-place upgrade.  You can then upgrade to 1511.  Keep only one cpu until you are completely done.

 

You can stop your VM and copy the disk image file as a backup in case things go wrong.

 

Several things I found with the 1511 version:

- Some privacy settings are either added or turned back on if you turned them off.

- You can set a default printer, but the default printer will change to the last printer used based on a setting.

- There are some minor cosmetic changes.  Icons have been changed like the default printer icon.

- I had some issues with printer drivers and had to remove printers and their drivers and let them re-load.

I thought it was just me that was having he issues.  Thanks for the info. I will try tomorrow.

Thanks for the help! Running with one CPU worked for me.