Windows 10 upgrade from Windows 7 killed Grub booter. Windows 10 won't launch

Hi Bob,

Thanks for posting your query on Microsoft Community.

To assist you better, please provide few details. 

1) Do you have dual boot on your computer?

2) Did you receive any error message, when Windows 10 fails to launch?

I would suggest you to download the media creation tool to install windows 10 and create Windows 10 installation DVD media and try Repairing your Computer.

Follow the below steps:

1) Create installation media for windows 10.

Refer to the below link:

http://windows.microsoft.com/en-us/windows-10/media-creation-tool-install

2) Insert the Windows 10 installation DVD in the DVD ROM and restart your computer.

3) After you boot your computer using Windows DVD or System Repair Disc, a black screen appears with gray text "Press any key to boot from DVD". Press any key.

4) Select the correct time and Keyboard type.

5) Click Repair your computer in the lower left corner.

6) Follow the on screen instruction.

Hope it helps, reply to us with the status of your issue. We will be happy to assist you.

After an upgrade from 7 to windows 10 while I had a Linux Mint 17.1  installation on another partition I had the same kind of problems. Suddenly my Grub bootmanager was missing and it wasn't possible anymore to get to the partition where my Linux Mint files were installed. I searched on the internet and found out that I wasn't the only one who had encountered these kind of problems. The partition of Linux suddenly had become unallocated space and couldn't be read anymore.

There were offered many solutions but most of them were not very clear to me. One of the advices was to try a program as Testdisk which had been a solution for many so I tried that first.

With Testdisk I discovered that at least the files of my Linux installation still were there. It even offered the possibility to copy those files to paste them on an external hard drive but when I tried that I couldn't find that hard drive with the program installed on Windows, and when I tried it with a live CD I could find my external hard drive but when I pasted the files nothing happened.

So I looked further for another solution. I tried Hirens Boot Disk, I tried Easus recovery  but they didn't gave me the solution for my problem. They couldn't recover my lost files or restore the linux installation,

Then I read about another recovery tool called Free Minitool Partition Wizard and I decided to give this a chance.

I installed it on Windows 10 and ran the program. It offered me the possibility to recover the Linux partition by first marking the unallocated space where my Linux Mint installation should be and then after first a quick scan run the Partition Discovery Wizard on the left side of the window. First I had to mark ALL the unmarked boxes of the partitions it had found - also the ones with the Windows Installation on it -  and at the end I only had to push on apply. Much faster than I had expected it was finished and the unalllocated space was again a partition with EXT4 on it.

That gave me hope again. After that I used the Live Linux Boot Repair CD to reinstall the Grub which I needed to get the choice again to boot into Linux Mint whenever why wanted. To be sure I checked - after I had booted up my PC with that Boot Repair CD - if I could read the files ( and back up them at once )  and I could. I made the default repair offered by that CD and when I booted up again the Grub bootloader AND my Linux Mint installation were there again.

I hope people who encounter the same kind of problems as I did will find any help in this post of my experiences  because the most solutions for this problem offered on the web untill now weren't enough to get me out of this problem because I an prpbably not geeky enough to understand.