Apologies for reviving such an old thread, but the OP never posted back with his results. I would like to post mine if that's alright (:
Going from an OEM installation of 8.1 Core, tweaking the registry settings suggested by gregrocker, I was able to use 8.1 Enterprise VL media to perform a repair installation and preserve all the user files, OEM software, drivers
, etc. Windows is now activated with VL key just fine.
I hope this will serve as a helpful reference for anyone who needs to accomplish this. I have been having all kinds of issues getting sensors and features (auto-rotate and WiDi) to work after a reinstall on all sorts of devices, and I am of the belief that many OEM installations are tweaked in such a way that an end user would not be able to replicate the changes needed to get things functional again. This has solved many of my problems in that arena, so thanks be to you, gregrocker!
As for the repair installation, you can refer to brink's walkthrough here: Repair Install Windows 8