!rant
Question...

I have a Windows 10 installation on my laptop...
A few weeks back my father bought an SSD for his Lenovo ThinkPad T500. Problem was - I couldn't install Windows on that laptop due to legacy BIOS (the T500 is old but gold). My solution was that I put the SSD into my eSATA portable HDD / SSD rack, and I installed Windows to the SSD on my laptop. It worked, but now, when I boot up my laptop it always asks which Windows do I want to boot up (only one Windows is present - the other throws an error). I switched the defaults, and now it boots up fine, but that choice really slows down my usually fast SSD boot (it has a 10 second timer before automatically chosing the default option).
How can I reconfigure it?
Or is it only possible by a clean install?