From what I've read, Windows 7 runs off BIOS and my system uses UEFI.
On, no and yes, mostly no.
- Windows 7 can be installed using a classic firmware (BIOS) with a disk partitioned with MBR.
- Or you can use the more modern firmware (EFI) and use a GPT disk.
You cannot swap between those. Installing in MBR mode and then moving to an EFI setup will not work. Neither the other way around. Use whatever settings you used for the old setup.
Note that many modern EFO firmwares support a legacy mode. This is likely what you enabled when you
selected the Legacy only in the EFI.
A second no because moveing an installed windows OS from one computer to another is not likely to work if the hardware is different. Windows tries (and is) smart about hardware and does some smart things in order to boot fast. But that also ties it to some hardware.
This comes down to:
- Either it will not work (e.g. when the HDD controller for the old system was different and the new controller is not recognised. So windows canot boot until you replace some drivers. Which is a catch-22
- Or it will work and you end up with a system which needs massive updating.
Option 2 is likely to be accompagnied with needing to activate windows again (and hopefully you bought a full license in a shop for a windows version which allowsyou to install it on another computer. Moving the license from the Lenono setup is likely not allowed if it is a Lenovo OEM license).
And maybe to late for this time, but for completeness sake: It is possible to move windows between hardware. Usually this is started with
sysprep which cleans out old drivers, sets compatability drivers etc. That is not an option unless your old system is still running since you need to do that before moving the disk.