Install windows 8, 8.1 and related windows server 2012, 2012 R2 without a product key

You have to edit/create the file disk:/sources/ei.cfg

[Channel]
Retail
[VL]
0

[Channel] can be set to OEM / Retail
[VL] means Volume Licensing for volume media for companies that use same key
[EditionID] to Core / Professional etc or leave black and it will ask during setup

To activate windows after install use the wizard or cmd : slui 3

To add the file to the windows iso file you can use PowerIso - note you need regiestered version.