I have Windows 10 pre-installed and then installed Grub with Ubuntu. Ubuntu is not my thing so now I want to remove it along with grub. How would I remove grub and make my PC use the Windows bootloader instead? I already removed all of the ubuntu partitions, but ubuntu is still an option in the boot menu however, trying to boot to it, and booting normally gives a grub command line. The only way to get Windows is to f11 into boot menu and pick Windows.
Seeing as you've come this far, why not try a different flavour of Linux instead?
If your reasons for not wanting to keep Ubuntu are because you don't have much space on your Hard Drive and can't spare 20Gb or so for another Operating System alongside Windows, then fair enough.
If, however, it's mainly because you don't really like the Ubuntu user interface then you might be pleasantly surprised by one of the other Ubuntu flavours.
I've been trying to find something similar to Windows for my folks to use and the default version of Ubuntu is a bit too different for them to be comfortable with.
Recently, I tried out Kubuntu and I think they'll like it because it's got a Start menu and displays the open windows at the bottom of the screen in a way that's much more familiar for a Windows user.
But onto your problem:
I suspect that Grub is throwing a wobbly because the partitions that were there when it was installed have been removed. Installing another version of Ubuntu will reinstall Grub and should resolve this issue.
Here's my recommendation:
Take a look at a few videos of Xubuntu, Ubuntu Mate and Kubuntu and see which one appeals to you the most.
Install one of them alongside Windows and keep it as a spare Operating System that you can play around with when you feel like it.
You might start to use it a bit more or you might not, but it's handy to have in case something goes wrong with Windows 10 and you want to still be able to use your machine whilst you're trying to fix the problem with your Windows installation.
If you're favouring Windows in this dual boot setup, then you can change a few lines in the /etc/default/grub file and have GRUB choose the last Operating System you booted as the default instead of having to select Windows from the menu each time.
Specifically, you would change GRUB_DEFAULT to read as GRUB_DEFAULT=saved and add the line GRUB_SAVEDEFAULT=true
Your pre-installed Windows 10 will almost definitely be using UEFI, so you need to make sure you install your Ubuntu flavour in UEFI mode as well.
Pressing f12 (or your machine's equivalent - maybe that's the f11 you mentioned?) when powering on and trying to boot from USB should bring up a 'One Time Boot Menu'.
This lets you choose to boot the USB in UEFI mode and will ensure that your Ubuntu flavour and GRUB are installed in UEFI mode too.
(I've installed an Ubuntu variant before and not chosen this option and it means that Ubuntu and GRUB are installed in 'Legacy' mode. Then, when you select Windows from the GRUB menu, Windows won't allow it because a 'Legacy' bootloader is not allowed to boot a UEFI Windows installation.)
If none of that appeals to you then there are a few other options:
Search for how to update GRUB from a Live Linux USB (make sure to boot it in UEFI mode). It won't remove the bootloader but if there's only one Operating System on your Hard Disk (now that you've removed the Ubuntu partitions) then the GRUB menu won't even show up because there's only one choice.
There's a program called Boot Repair that is probably the most straightforward way to do this: How to install the Boot-Repair tool in an Ubuntu live disc?
If all else fails then you could try going into the Settings on Windows 10 and choose the 'repair' option and see if that works out.
Use windows recovery options in windows 10.
Look here in the microsoft website: https://support.microsoft.com/en-us/help/12415/windows-10-recovery-options.
Do a startup repair and windows will clear away grub and repair its bootloader.