I will post my experiences here too (most popular topic on hddhacking):
Basically after migrating from 20g to 120g with official MS cable my xbox1 originals became non-working.
The error message was:
"The game could not start. Please download the game again."
MS support could not help me.
All Xplorer360 versions had serious problems with my 120g Elite hdd but I could see that partition2 was missing.
To be short: if you have such problem and want an easy solution:
- get Xplorer360 xtreme2 somewhere
- connect your HDD to the PC
- in Xplorer360 select "restore partition 2" and browse the file I linked .... voila!
partition2 image which contains the 2007-11 xbox1 compatibility update:
CLICK HERE---
Thank you 'The Specialist' for Xplorer360xtreme2

!