I decided to revamp my hard drive partitions and replace Linux Mint with Manjaro, since I was craving that new distro euphoria. I actually have two hard drives, and one of them was going completely unused, while the other one was split between Mint, Windows and a common files partition. I figured it would be a nice call to use my secondary, smaller HD for Manjaro and leave the main one for Windows and common files only.
So I went ahead, dd'd that .iso to a USB stick, and installed it smoothly. But alas, I can't boot into Manjaro - Windows takes over before GRUB even gets a chance to show its face to me. So I go, boot with the USB stick again, triple-check to see if everything was still there, reinstall and update GRUB, check grub.cfg, everything was in order. But still no GRUB menu.
Then it hit me - it's installed in another hard drive. Yes, I missed the most obvious of all.
A quick change to boot devices in BIOS got me just where I wanted to be. Just thought I'd share this with y'all, in case anyone runs into a similar problem and, like me, misses the most basic setting of all.