The repair program is backward compatible so it will work on all versions of Windows, although it has given problems on Vista x64 bit I believe.
Do you have Win 10 install media or access to another Windows machine to create Win 10 media ?
You can create Win 10 install media after reading the instructions at
https://www.microsoft.com/en-gb/software-download/windows10If you are using a machine that uses an UEFI BIOS then you will need to go into that to disable Secure Boot if you are using an USB for the install media.
If you are able to create the Win 10 install media, tap F12 as you switch on the affected machine (insert the USB first if using an USB) - use the cursor keys to select the mode for the media you are using, insert the DVD if using one of those and press enter.
If using a DVD then press any key when prompted to boot from CD/DVD where you may be presented with an inverse window with Windows Setup [EMS Enabled] highlighted - just press enter.
Change/confirm the keyboard and currency then click on Repair your computer on the Install screen.
You only get two options to get started again, Start-up Repair or System Restore.
I'd try the System Restore to use your restore points which will be prior to you running the repair program.
I've emailed Shane about this as yours is the second recent report about a machine not starting after running WR.
Do you know what was wrong with the machine prior to running the repair program ?