Hello,
Well I ended up checking to see if Secure Boot was in my BIOS. It is not. However, I double checked all other Windows specific features or boot features and made sure they were disabled. Unfortunately, it did not solve anything.
However, I have found a solution. Granted this would be easier on a fresh install, I didn't want to deal with Windows 7 support telling me my key was an upgrade key only, so this is what I did.
I turned off my PC and unhooked the Ubuntu and Windows 10 drive and any storage drives or USBs. Next, I booted into Windows 7 recovery using my DVD. I selected "Repair this computer" and then selected my Win7 OS from the list of Windows 10 or Windows 7. Next, I opened the command prompt option and started a boot repair on it using these commands so that I could boot into the OS again:
Code:
Step 1: bootrec /fixboot
Step 2: bootrec /fixmbr
Rebooting allowed me to access Windows 7 from BOOT menu on my BIOS (by pressing F11 and selecting the Win7 drive manually). Now I needed to get rid of the black grub menu that was preventing me still from booting normally into Windows 7, but first I needed to also get rid of the Win10 garbage left behind, so the next thing I did was log into Windows 7 and open MSCONFIG with Windows Key + R. In here, I went to BOOT and selected the leftover Windows 10 and deleted it, applied and then exited out without a reboot.
Next, it was grub removal time. I had to navigate to the EFI ubuntu folder on the Win7 drive and delete it. I did this by opening CMD as admin. I'd detail this part, but I'd butcher it, so instead I'll link to the post that I followed:
You will be doing this from Windows 10. No bootable media required.
Where bootrec /fixmbr, bootsect /nt60 and the Ubuntu live with the boot-repair suggestions have failed, this has worked for me:
(This answer borrowed verbatim from
here)
- Run a cmd.exe process with administrator privileges
- Run diskpart
- Type: list disk then sel disk X where X is the drive your boot files reside on
- Type list vol to see all partitions (volumes) on the disk
- Select the EFI volume by typing: sel vol Y where Y is the SYSTEM volume (this is almost always the EFI partition)
- For convenience, assign a drive letter by typing: assign letter=Z: where Z is a free (unused) drive letter
- Type exit to leave disk part
- While still in the cmd prompt, type: Z: and hit enter, where Z was the drive letter you just created.
- Type dir to list directories on this mounted EFI partition
- If you are in the right place, you should see a directory called EFI
- Type cd EFI and then dir to list the child directories inside EFI
- Type rmdir /S ubuntu to delete the ubuntu boot directory
Assuming you only ever had two operating systems (Win 10 & Ubuntu) you should now be able to boot directly to Windows without hitting the black grub screen.
Source: https://askubuntu.com/questions/4296...ows-bootloader
I'm sure you can probably do the same thing from a DVD for Windows (and I did this in Windows 7, not 10, so it works either way), but thankfully I could get into my drive to do it from the OS.
Now, to get the original functioning grub so I didn't have to boot twice into whatever Windows OS I selected. The problem was installing Windows 10 last beforehand, triggering it I guess to make its own boot menu on top of grub. I achieved the fix by doing this:
1. unplug all drives EXCEPT the one drive with Windows 10 on it that I would be reinstalling over / the drive I intended to use for Windows 10
2. boot up UEFI USB I made with Rufus
3. Reinstall Windows 10
With Windows 10 done and my Windows 7 install fixed and no longer attached to Windows 10 or grub, I powered off again. I unplugged Windows 10's drive and then plugged in the drive I wanted for Ubuntu back in, making sure it was the only drive hooked up. Booting up boot-repair could not save her though, so I had to reinstall. Unfortunately, I ran into a slight hiccup as my installer crashed once. So I rebooted back into the Live USB and clicked the Try Ubuntu Before Installing again.
This time I opened up gparted and deleted the Ubuntu partitions so it was one unallocated space. Two minor partitions refused to delete though, so I had to right click them and click SWAPOFF. It then allowed me to delete all partitions. I applied the actions by clicking the green check mark and then began the installation process again.
Once it was finished installing Ubuntu, I shut down the computer and plugged in the Windows 7 and Windows 10 drive and booted back up. I was instantly logged into Ubuntu, which is what I wanted. If one is not booted into it, you can manually boot into Ubuntu by getting into your BIOS boot menu.
Inside of the fresh install, I installed boot-repair and grub customizer.
Code:
sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair
And
Code:
sudo add-apt-repository ppa:danielrichter2007/grub-customizer
sudo apt-get update
sudo apt-get install grub-customizer
Next I opened up boot-repair and did the recommended step option. It had me do some terminal manual steps, like deciding where to place my grub, and then I was done. Without rebooting, I closed down the boot-repair pop ups and then opened grub customizer.
In here, I had a whole slew of options, most with the crazy looking bootxx.efi and other efi files. I clicked one of them, right clicked and created a new sub-folder and moved all of those crazy options into it. Next, I located the boot entries that would take me into Windows. For example, mine were;
Windows Boot Loader (/dev/sdX)
Windows Boot Loader (/dev/sdX)
*where x is each separate drive/install
I knew where I installed Windows 7 too, so I knew the first dev/sdx was my Win7 and so the other was Win10. So I double clicked them and renamed them to simple things like "Windows 7" and "Windows 10". If anyone reading this cannot figure it out or remember where they installed, you can reboot here and boot into each entry, remember which you booted into, and then recording it down so that when you boot back into Ubuntu for this step, you can appropriately rename them! 
I then pressed the Save button and opened a new terminal and updated the grub:
And then I rebooted, and I had a simple purple grub menu again and I didn't have to deal with the double booting for Windows (I blame Windows 10 entirely for that headache!) and they were all still UEFI!
Obviously if you are starting fresh rather than trying to save an OS like I needed to for Windows 7, you just install each OS separately as UEFI. This means unplugging all other drives and then when you move to the next OS, unplug the previous OS drive and so on.
Well, I hope this helps others who triple boot like me and came across this, or anyone at all.
P.S
Sadly I have found that in UEFI mode, one cannot use ext2explore on Windows to explore the Ubuntu drive any further! OUCH! 
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Re: Triple Boot UEFI Problems [requires a second boot on grub]
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