1. re66's Avatar
    I have installed a win 10 on my win8.1 computer on differant partition.

    After few days win 8.1 say that my activation key is wrong and I need to reactivate.

    I'm affraid that reactivation will only after my next win 10 upgrade ( probably reseting key in the bios )

    What can I do ?
    09-18-2015 01:17 AM
  2. TechFreak1's Avatar
    Hmm, I'm guessing your Windows 10 version is still activated?
    Try the change product key option under Control Panel\System and Security\System and put in your 8.1 key again.
    You might need to call them and tell them you're trialling hence the dual boot which I imagine is true as after all why else would dual boot, right?

    If however your Windows 10 version is not activated, what would need to is clone your 8.1 install onto another hdd, upgrade, clone the upgrade into the Windows 10 partition where it is currently installed. However this method is extremely risky as you may need to fiddle around with BCDedit to get dual boot working properly again.

    Not to mention if both installs have to be using GPT or MBR, you can't mix and match.

    EaseUS Disk Copy Freeware - Free Disk Copy, Disk Clone Software download to Clone Hard Drive You can use this, that is what I use personally as it's free and will need to clone everything. Cloning partition by partition for what you need to do won't work as you need the bootfiles and the master boot record.

    Alternatively you could try cloning the W8.1 partition on the same hdd but I would not recommend that at all as you will need to reinstall everything from scratch if either bootrec\rebuildbcd, fixboot, fixmbr commands do not work via the recovery console.

    I would suggest getting familiar with these and BCDedit - here are some handy links to get you started.

    https://technet.microsoft.com/en-us/...(v=ws.10).aspx

    bcd - How to use BCDEdit to dual boot Windows installations? - Super User

    How to fix MBR through command prompt? - Windows 7 Help Forums

    How To Rebuild the BCD in Windows [10 to 20 Minutes]

    Fixboot Command (Recovery Console)
    09-18-2015 03:32 AM
  3. Steve Thackery's Avatar
    Surely, if you obtained your W10 license using the free upgrade route, then you are breaking the terms of the license to keep using W8.1 as well.

    What you get for free is an UPGRADE from W7/8.x to W10. You don't get to keep your old W8.1 installation as well. Microsoft are giving W10 away for free because they specifically want you move you away from W8.1, not keep it as a second OS. If you want to keep your old 8.1 installation, you are supposed to buy a new W10 license, which I think costs about $100.

    So although TechFreak's solution is probably viable technically, I don't think it complies with the terms of the license.
    09-18-2015 07:39 AM
  4. TechFreak1's Avatar
    Surely, if you obtained your W10 license using the free upgrade route, then you are breaking the terms of the license to keep using W8.1 as well.

    What you get for free is an UPGRADE from W7/8.x to W10. You don't get to keep your old W8.1 installation as well. Microsoft are giving W10 away for free because they specifically want you move you away from W8.1, not keep it as a second OS. If you want to keep your old 8.1 installation, you are supposed to buy a new W10 license, which I think costs about $100.

    So although TechFreak's solution is probably viable technically, I don't think it complies with the terms of the license.
    Steve, there are three ways to get a valid license 1) Having participated throughout the insider programme and your running build 10240 2)Via the upgrade and 3) a purchase. OP's most likely running the 1st option so technically the setup is legit, that is the only way to dual boot without going through what I said previously.

    I imagine he/she hasn't gone through the upgrade otherwise he/she wouldn't be asking. Also you only have (I believe) 30 days to roll back. Furthermore you get a brand new key when you upgrade to windows 10.
    09-18-2015 08:58 AM
  5. Peter McNeill1's Avatar
    While you get a new key when upgrading to Win 10, the old key is mated to the new one and rendered invalid so you can't reinstall Win 7/8/8.1 anymore with the old key. You'd have to buy a new 7/8/8.1 key.
    09-21-2015 12:32 PM

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