Same here. I installed Linux Mint on my internal D: drive and left my Windows C: drive completely untouched. Then, I changed my boot order in bios to boot from drive D: This lets you play with Linux without messing with the bootloader on your Windows drive, or fiddling with partitions.

Once I decided to keep Linux, I modified the D: drive bootloader ("sudo update-grub") so it would show both drives when I booted from D: Now I can boot into either OS without having to change the boot order in BIOS.

THIS all fucking day for new and even experienced users. Setting up a dual boot is fairly easy. But the moment you decide that you just need Windows (mostly new/non-tech users) and delete the Linux partition. Shit will break booting and lead to so much panic and/or frustration just getting Windows booting again. And that ignores the additional fuck-ups that can happen with just making a small mistake doing anything with partitions no matter the OS. It is much less frustrating to just disconnect the second drive in a desktop (or just format the drive and have as a data drive). Or to just swap one drive for another in a laptop with one drive bay/slot. Opening a laptop might be annoying depending on the model.

But at least your data and OS won't be lost. Lots of people can understand using a screwdriver and spudgers while watching a video and some care. But lots of video and written guides for complex software can be worse. Lots of my frustrations with Linux guides over the years has to do with some steps being just left out due to the person(s) showing or writing it just assume certain steps as being super "obvious" or "common sense." Though some folks are at least good at pre-facing stuff as assuming certain levels of knowledge. So it is easier to know that I might need to also research whatever they mentioned.

And if someone is experienced, it is still good to keep your OSes on physically different drives. Reduce the amount of problems that can come from a drive going bad and taking both (or however many) OSes down together. Of course backups are to be made for reasons that include a drive failing. But shit happens, and minimizing impact and the work needed to get everything working again is always a good idea. It is also nice to know that if you get the itch to distro-hop, you can just nuke the one drive without worry as much as you want. Keep your "I need to know this won't be impacted" drive safe, and your play drive liquid.