Computer boots automatically into GNU GRUB, no other options

Here's what worked for me. First of all, to quit GRUB2, if I ran exit twice, my computer would finally boot into Windows.

I then had to go to my UEFI settings:

• Open charms bar (swipe from the right in)
• Click Settings
• Change PC settings (located at the bottom)
• Update and Recovery
• Recovery
• Under Advanced Start Up, click Restart now

Once there, I was able to open the Boot menu from under the advanced options and I deleted the ubuntu entries.

Afterwards, I reinstalled Windows, though I don't think that's necessary. If you want to reinstall, that option is also under the PC Settings -> Update and Recovery -> Recovery.