As I mentioned in an earlier post, I had planned to install Windows 10 on a new directory, with the free install, and failed.

And although the plan now is reportedly to provide a version for next month that will allow this I decided to give it another try.

Short answer: You CAN clean boot a new copy of Win10 using your old OS free upgrade offer, AND dual boot to the old one and Win10 both.

Long answer: You really, really will not want to. It is time consuming, tedious, filled with little ‘gotchas’ that will have you pulling out your hair, and frankly the end result isn’t worth the aggravation (I have to test software on Win10, so I’m stuck).

Enjoy misery? Then abandon hope, all yea who continue reading:

1. I had a spare Win8.1 directory I never used, as real programmers all do (real programmers use the oldest operating system available when developing, Win7). After my Win7 install failed (fortunately, as I – and you – are soon to find out), I decided my nearly-new install of Win8 should work fine. From there, once Win10 was installed, and my key was validated, I could do a clean install on a new partition, and then restore Win8.1 to the way it was.

   ‘Before’ Me was so naive…

2. I thought it was overkill, but decided I’d backup the Win8.1 directory (tip for everyone – install Windows on a one smallish partition, and keep all your data on another partition. Then you can blow away Windows anytime you want and keep all your vital docs, files, etc. It’s time-consuming to set up, but in my years of programming, I’ve never encountered a better trick for working with Windows). For the backup, I used Macrium Reflect, free for personal use. Since Win8.1 was fairly pristine, the backup was fast.
3. From Win8.1 I ran the setup from the USB I had (made via the Media Creation Tool from MS). One tip: Make sure the version/bit size matches your install – in my case, I could use ‘Pro’ and 64 bit. Don’t forget, for an update you run it from within Windows.
4. After a bit of questioning (skip the key entry – always!) the install went along. Bring a book, game or find something else to do – I lost track of time, but altogether hours will pass…
5. Eventually, I was done. I checked Win10 (via Setting/Updates) and it said I had Windows installed – great. According to all I had read, this now licensed my computer to the Win10 copy, so I was good to go. On to the clean install.
6. For the clean install, I had a new(ish) drive that was waiting for it. I put the USB in, rebooted, and then went to my computer bios menu (or whatever it is called these days), and selected to boot from USB. It started the install, allowed me to pick a partition, and after some (a lot of) time, failed with a message “Windows 10 cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks.” OK, I was using an older drive, so maybe my other drive (where I had just placed Win10) would work (note to self: I apparently have an EFI system).
7. So, I then spent a long, long time finding room on the drive. Copying files over to the other disk, and then using Disk Management to shrink and move around partitions. After literally spending decades on it until I had a biggish partition ready for clean Win10 install…
8. …and it failed with the same message. Back to Google (isn’t there a bit of irony in using Google to solve Microsoft’s problems?) And I finally found a note that the way the USB boots determines the media it installs on. I dug around and was finally able to find a boot selection from my BIOS that booted it the ‘other’ way – and that did the trick. Not only that, but my original disk choice could now be used for the install. Sure, the messages seemed downright naggy, like what I was using my computer for (and it again asked for the license key, which I continued to skip), but it went ahead and did a proper, verified (via Settings) install.
9. Now with Win10 finally done, I could restore Win8.1 via the recovery option. And it chugged along restoring – until the message “We’re sorry, but you can’t go back. The files we need to take you back to a previous version of Windows were removed from this PC” Now I don’t think they were really sorry, just smarmy (like they’d been all along); plus all the files were still there (Windows.old, $Windows.~BT, $Windows.~WS, etc), but they say no, so it’s no. Most of the Internet told me the problem was I had passed my 30 day window, but everything was less than a day old. My guess? The second install ‘tweaked’ things – whether deliberate or not I cannot say (though I have my suspicions) – to make sure I couldn’t roll back.
10. But thanks to Macrium, MS was thwarted. I restored that partition to Win8.1 via the backup, booted into it, then booted to Win10 and Win7 to confirm all was well. It was, with one little detail: The boot manager still showed Windows 10 in the menu for Win8.1, so I had to use bcdedit to VERY carefully rename it to Win8.1 again.

And that’s the tale. It is possible to clean boot without losing your old OS on the free offer – kinda. I actually lost it thanks to MS, but because of backing up, I was fine after. I cannot emphasize enough to back up beforehand, and set up multiple partitions for your OS, so you can easily plan for this. And this is a testimonial to the fine folks at Macrium – great tool (and if you ever want a review – contact me).