I've got plenty of test machines to do this on and get this figured out. There have never been any complaints about the performance after using this workaround which has been used countless times since Win7 release to change between version, including from beta. Apologies for reviving such an old thread, but the OP never posted back with his results.
I'm determined to make this work but I need some help. 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. I hope this will serve as a helpful reference for anyone who needs to accomplish this.
WD1001FALS Internet Speed 15/2 cable modem Other Info Windows and Linux enthusiast. There is a workaround to change between versions which has been used successfully here for years now, including by tons of beta testers changing to their paid version of Win7.
It tricks the installer into thinking it's doing a same-version Repair Install which is always allowed, since no other in-place Upgrade path is available for Win7.
You could experiment with a single unit to see if it will work then write a script or Sys Prep to mass deploy, since your only other option is apparently to clean reinstall all 400 computers.
The important thing to remember when mulling this is that a Repair Install completely reinstalls the OS so there is no trace of the old OS left, but leaves your files, programs and settings in place.
However this has never been tried that I know of to Enterprise which has its own licensing scheme.
I doubt licensing comes to bear while changing the OS over, however, but would be done later with the new method.
There HAS to be some way to script it or upgrade it without having to re-install the entire OS.I have more than 400 computers that have 7 Professional installed and need to be upgraded to Windows 7 Enterprise.I have done some research and so far i found out that its not possible to do so. Computer type PC/Desktop System Manufacturer/Model Number Ignatz Special; 4 speed manual gearbox; factory air conditioning; one of one OS Windows 7 Home Premium SP1, 64-bit CPU Intel Skylake i5-6600K, not overclocked Motherboard As Rock Z170M Extreme 4, micro ATX Memory 8 GB Hyper X DDR4-2666 (2 x 4 GB) Graphics Card none; graphics are integrated on CPU Sound Card onboard: Realtek ALC1150; external: USB Behringer UF0-202 Monitor(s) Displays Dell S2340M 23 inch IPS Screen Resolution 1600 x 900 Keyboard Microsoft 200 6JH-00001 USB Mouse Dell or Microsoft optical wired; USB PSU Rosewill Silent Night 500 watt fanless, semi-modular Case Antec Solo II Cooling Noctua NH-U12S; Noctua F12 intake, Noctua S12A exhaust Hard Drives System: Crucial MX100 series SSD, 128 GB; Data: Samsung Spinpoint 103SJ, 1 TB; Backup: WD Caviar Green WD30EZRX-00D8PB0, 3 TB Antivirus Microsoft Security Essentials and Malwarebytes Premium Browser Pale Moon Other Info All fans PWM; speeds at idle: CPU circa 500 rpm; intake circa 600 rpm; exhaust circa 600 rpm; CPU temps 27 idle and 47 C load in a warm room (27 C/81 F) when running Intel Extreme Tuning Utility stress test.As for the repair installation, you can refer to brink's walkthrough here: Repair Install Windows 8 I know this is an old thread, but I found it very helpful and wanted to report apparent success upgrading a Window 7 Professional install to a Windows 7 Enterprise install.(and then successfully activating the upgrade via KMS to utilize our Enterprise license) Did two Lenovo laptops.