2nd SSD causing issues - after a recent change

[FingertipPhil]

My mate gave me a tower with some bits n bobs in ram, processor etc. But it didn't really work out. As I'd already installed my fx card, and both SSD's in the new tower I changed them back over, to my old system but I now get this message on start up when both SSD's are in. (They are SATA - the 128gb has win 10 in it, properly partitioned - the other large one just has games and other software on it.) when the 128gb is installed on its own, it's fine but when I got both - I get "attempted to boot UEFI volume from legacy mode" when I remove the larger SSD windows will load in no problem.
Trouble is when I got into BIOS UEFI has no boot options. I'm not all that au fait with motherboards so any help would be great

 

[geofelt]

You probably have some residual boot data on the big ssd.
Perhaps a residual hidden recovery partition or such.