Repair Win 10 boot

From a couple of questions recently about reinstalling and dual booting with windows 10 ... plus a post I made about the "default" partition(s) the installer/upgrade creates ... I've done a bit of digging ... and until I see this lot written elsewhere ... I'll claim that this is (at least one of) the definitive descriptions. Here we go ...
These are the default partitioning patterns and sizes you will probably end up with by default.... Obviously the Win 10 partition is as big as you make it ...

Upgrades:
Win 7 to Win10 ... System Reserved 100Mb (NTFS) ... Win 10 (NTFS) .... Recovery 450Mb (NTFS)
Win 8.1 to win 10 ... System Reserved 350Mb (NTFS) ... Win 10 (NTFS)

Clean install:
NB; This is starting from an unpartitioned Disk.
System Reserved 500Mb ... Win 10

Exceptions:
If the disk already contains any of the following; Factory created Recovery partitions, Hidden Windows Partitions, Linux partitions (Created by Linux O/s or Acronis or other partitioning recovery software ... It's possible that separate System reserved and/or recovery partition(s) will not be created.

Fixing Faulty Windows 10 boot or unable to boot option.
If the boot options create "unexpected" errors ... or the machine fails to boot at all ...
Either start Win 10
Or Start the windows 10 Install DVD (http://ift.tt/1M8RpCC) and use "Repair your computer"
From the menu : Troubleshoot | Advanced Options | Start-up Repair
(It's possible that you'll get an error message at this point - ignore it - remove the DVD and restart).
And that should be that... Win 10 should boot OK.

If It doesn't work ... or you're addicted to the command prompt - Troubleshoot | Advanced Options | Command Prompt

Enter the following three commands ( note it's bootrec<space>/rebuildbcd followed by enter)
bootrec.exe /rebuildbcd
bootrec.exe /fixmbr
bootrec.exe /fixboot
Restart your pc.

It's as easy as that!

Repair Win 10 boot