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Windows 7: Possible to use upgrade key with RTM install?

23 Oct 2009   #1

Windows XP Home
Possible to use upgrade key with RTM install?

Hey everyone,
I pre-ordered the windows 7 home premium upgrade from newegg. UPS said it would come today, but it didn't. My friend has an RTM disc. Is it possible to install home premium from the RTM disc without a serial number and then when my upgrade copy comes in, enter it without reinstalling?


My System SpecsSystem Spec
23 Oct 2009   #2

Windows 7 Ultimate RTM

If you're talking about the RTM version that was downloaded for those who were in the beta test, the answer is no, since that version was Windows Ultimate, and the key you have, or will get, will not work to install Windows & Ultimate. It sounds like you're just going to have to wait.
My System SpecsSystem Spec
23 Oct 2009   #3

Windows 7 Ultimate x64 (Retail)

Well, it is possible to install any version (not talking about 32 or 64 bits here) from any W7 installation media if you can do some editing (delete the sources/ei.cfg file) on the install disk. You have to mount it on a virtual drive to do the editing and then burn a new.iso w/o that file, or copy the modified install files to a bootable USB drive and install from that). But since your version is coming so soon, I would just wait.
My System SpecsSystem Spec

23 Oct 2009   #4



But -

The RTM disc includes a file named EI.cfg. It is necessary to delete/edit that file to enable the installation of the various versions included in the RTM.

Extract the ISO. Delete/edit the EI.cfg file (delete recommended here). Recreate the DVD from the extracted file set.

Post back if you require additional information.

harpua - the Antman is in slow mode.
My System SpecsSystem Spec
23 Oct 2009   #5


I've read reports of people using a "full" disc to install, but then a key from an "upgrade" disc not working to activate.

It's possible they indeed did something like installed the wrong version, BUT...

I'd wait for your own upgrade disc. There's indeed a possibility that (1) You'd have to reinstall Windows 7 entirely, and (2) you'd also have to reinstall XP or Vista first.

There's too high a risk of a lot of wasted time vs. just waiting another day or two and making sure it's done right the first time.
My System SpecsSystem Spec
23 Oct 2009   #6
Microsoft MVP

Windows 7 Ultimate 32bit SP1

As mentioned ... wait and take your time to install and activate the new OS *right*!
My System SpecsSystem Spec
24 Oct 2009   #7

Windows 7 Home Premium

I installed Windows 7 Home Premium RTM on my laptop (clean install, no product key). I ordered the upgrade from and was able to use the product key from the upgrade to activate the install. I was afraid I would have to reinstall Windows Vista to use the upgrade, or at the least, have to do a clean install from the upgrade DVD, but thankfully I did not.
My System SpecsSystem Spec
26 Oct 2009   #8

Windows 7

I installed the RTM on my netbook without activation. I now have my keys and tried to activate but get an error message claiming my key won't work with a clean installation only an upgrade. Microsoft tech assistance claims I just need to reinstall Windows 7 as an upgrade then it will allow me to use my keys. Unfortunately I only have a small SSD and it doesn't have enough room for the upgrade.

After some time with MS tech support they provided me with a solution that worked. I hope it can help someone else.

1) Open regedit.
2) Backup your registry.
3) Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup\OOBE
4) Change the key "MediaBootInstall" to "0".
5) Open a command prompt as administrator.
6) Type in "cscript.exe slmgr.vbs -rearm". Press enter.
7) Reboot
8) Enter you product key.
9) Relax knowing you didn't have to sit on tech support.
My System SpecsSystem Spec

 Possible to use upgrade key with RTM install?

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