Hopefully you are following my posts about Partition Sizes and know that the Windows RE tools Partitions are really too small to be usable. So what happens when you upgrade a Surface Pro to Windows 10? Nothing good.
Partition 1 – 350MB Windows RE tools
For starters, this partition is good enough for the default Windows 8.1 WinRE.wim, but Windows 10 kicks things up a with a WinRE.wim over 300MB. Since 50MB needs to be free for VSS, this partition fails and cannot be used for WinRE. What ends up happening is this partition is abandoned and not used at all.
Partition 2 – 200MB System
This partition works fine without issues.
Partition 3 – 128MB MSR
Partition 4 – Windows
This partition works fine without issues. It is a large Partition that is the remainder of the space of the drive.
Partition 5 – 450MB
This is a newly created Windows RE tools (although no label) Partition. While a new Surface Pro will have 5 Partitions, this 6th Partition is necessary for WinRE.wim (since Partition 1 was too small).
Partition 6 – 5200MB Recovery image
The Windows 10 upgrade creates a file in RecoveryImage\DONOTREPLACE.txt that is a marker for Windows Setup to leave the contents of this Partition alone. No other changes are made to this Partition. It contains the OS Recovery Image
So great. Now you have 800MB (Partition 1 350MB + Partition 5 450MB) being used for WinRE.wim, and your Partitions are not properly ordered anymore (WinRE.wim is no longer in Partition 1).
If Partition 1 Windows RE tools was 984MB (my recommendation), then the additional Partition would not need to be created.