I transferred the Windows 7-64 bit from one SSD to another SSD, it boots & functions except for 1 thing; Device Manager shows Error Code 10 (This device cannot start) on any & all USB Mass Storage DEVICES. Windows 10 on the same SSD & on the same computer does not have this issue. USB mouse works under all scenarios.

Don't think it's something to do with the difference in SSD's: Samsung 840EVO-120GB vs Samsung 850EVO-240GB.
2 Windows builds on a single 120GB fit, but with little room left over.
Am now back to using 2 drives: Samsung 840EVO-120GB & WD Scorpio Black 320GB.

I've tried all the "Code 10 Error Message" fixes & none of them work. Performing an OS repair may do more HARM than good. Anyway, Windows 7 will be upgraded to Windows 10 soon. This one REALLY has me baffled.

If nothing else, learned a lot about multiboot with BCD which is nothing like the old boot.ini. It does require a UEFI/BIOS instead of the old BIOS-only. Conversion from MBR to GPT works as does dual booting into either OS.
Interesting fact: If Win7 is the default boot, you get a DOS-type screen to select the boot, if Win10 is the default, you get a graphical screen.

BTW, 2 tools have been indispensable for transferring OS's & repairing BCD's:
1. Latest version of Macrium Reflect v6, WinPE boot disc. This one is good for restoring partitions from a backup drive & can fix boot issues.
2. AOMEI Partition Assistant, WinPE boot disc. This one is good for managing (copying) existing partitions.Last year when I was researching my SSD purchase (Samsung Evo 840) I saw a forum topic about USB Mass Storage Error 10 on Windows 7 new install, and the culprit was Rapid Mode in Samusng Magician.

http://www.techspot.com/community/topics/new-win7-pc-usb-storage-device-driver-code-10.206770/
Thanks. I figured it had to be something to do with Magician. Didn't make sense how it would have any affect on USB.
Right now, I have the 840 installed; Rapid Mode is enabled. Also have INTEL RST enabled.
Magician has this note on the Rapid Mode page:

Limitation: RAPID Mode only accelerates one SSD, even though the system may have more than one supported SSD.

I'll have to try it again sometime.

BTW, I did notice that the Magician TRIM feature was disabled for Win10 since it is supported natively.