Yes... the app WILL NOT do this for you. If your older BiOS just happens to be set to UEFI-CSM (an older mode that could do both), you may be alright... better know ahead of time and have a good backup just in case.
I guess my next question would be... why do you feel you need to go to UEFI BOOTing? Does not the existing Legacy BOOT work just fine?
I guess my next question would be... why do you feel you need to go to UEFI BOOTing? Does not the existing Legacy BOOT work just fine?