I would like to know if it is possible for me to install ElementaryOS alongside Windows 10 but not replace or touch my Windows 10 bootloader at all.  I don't want to turn my computer on and see a GRUB screen asking which OS I would like to boot to, I want to be able to have GRUB on a thumb drive so whenever I would like to boot to Linux I can just plug in a thumb drive, select it in BIOS and go from there.  IT doesn't like Linux so I need to make sure they don't discover it exists by accident.  I can hide that partition from windows explorer in the registry, so all that I have to do is hide it from any bootloaders.  Does anyone have any suggestions? Thanks!
Can I install linux on my HDD and GRUB on a thumb drive?
dual boot;grub;elementary os
Yes, it works, I have a similar setup. First make sure you make a backup of the original master boot record before you start (and after you repartitioned the harddisk), just in case.Then it's only a matter of installing the grub bootloader to your USB stick and change the BIOS settings to have the USB stick with higher priority than the harddisk.