I will give my answer as follows:
When installing Linux Mint 18.3 Sylvia (Cinnamon) onto a machine that has nothing (no windows, linux, or mac), I would suggest doing the following:
- Use GParted to establish an MSDOS boot sector (can be small or large, even as small as < 50MB probably, mine was 400 MB, depends on your grub, etc.. situations). Mark the boot sector as boot in the manage flags. And then it's fine to set the rest of the hard-drive as ext4. NOTE: This step MIGHT be optional but the install seems to go better if you do this first.
- Burn an image (ImgBurn does the trick fine) of the downloaded .iso for Linux Mint 18.3 (your appropriate number of 32 or 64 bits of course, and amd, etc..).
- Then try to install Mint by booting to that DVD. If you wind up with a login screen and mint is the user - you probably have a bad DVD. I would suggest running the "Check Integrity" install option and see how many errors you got - I got one in my case but that was enough to mess up my install. The install should simply give you a desktop that allows you to proceed with the install.
- When you install, the simplest way to guarantee success is to choose the top-most radio button to reformat everything.
Note in that above that it is NOT necessary to make your cd/dvd/usb cd/dvd as the first bootable, since you can click on F12 (or your bios's boot setup key), and change it for each boot, that way, your hard-drive will be already
selected as the first boot drive when you succeed and it reboots for the first time with the new operating system.
Your mileage may vary, but this should help with installing Linux Mint for people who have had a bad experience with login prompts and just couldn't get past that screen. It's probably best NOT to even try to go past that screen as you may have a corrupt image. I don't know exactly why a corrupt image behaves that way - I would think it would fail in other ways - so perhaps there is a deeper understanding of this process than I can offer at this time. Good luck!