This is the joy of Windows 10. It appears it has claimed another laptop. Your best bet is to ride this out. The only other choice is to try going back to the original OS but you will lose everything if you try to soon. If it ever gets done with the reverting and you still have 10 then you should make backups of your files and then go back to your original OS. If it never finished then you are going to have to jump thru hoops to get your files back. The info might help you if it never finishes the reverting.
The first thing you want to try to do is run a Windows System repair disc or thumb drive to see if it can fix the problem. With any luck it might find a problem it can repair. If you do not have one and can find someone who has the same version of Windows you do then you can use the link below to make one.
For Windows 8 and above systems.
http://www.howtogeek.com/131907/how-to-create-and-use-a-recovery-drive-or-system-repair-disc-in-windows-8/
You can also try this to get a repair thumb drive.
To get a bootable thumb drive to boot Windows 10 to try to repair it you need to download the Media Creation tool. Go to the link below and scroll down and click download tool now. Once downloaded make sure you have at least a 4GB thumb drive plugged in. Right click the Media Creation tool and then click run as administrator. It will ask what you want to do and click Create installation media tool for another PC. The next Window will ask what language and other info. Put a check in the Use the recommend options if they apply to you. If you are in Europe select Windows 10N. The next window will ask where you want to download to, select USB flash drive. The program then will download and configure the thumb drive to help you repair your current version or do a fresh install if worse comes to worse.
https://www.microsoft.com/en-us/software-download/windows10
Once you have the thumb drive create you can now use it to boot your lappy and try to repair your boot problems.
If that does not work, the the next thing is to try to recover your files. For this you will need a bootable thumb drive(flash drive) so you can boot the lappy. This will also allow you to verify that the lappy and its hard drive is good and all you have is a Windows problems. To boot the system you need to make a bootable thumb drive. You will need to find a working puter to download Unetbootin USB installer. You need to read the instruction carefully and know a little about Linux to use this. There can be dragons present if you do not understand what your doing. I make no guarantees.
http://unetbootin.sourceforge.net/
Once you make the bootable thumb drive you need to add a OS for it to boot. I recommend Linux Mint ISO. Its UI is similar to Windows. Download Cinnamon 32bit.
http://linuxmint.com/
If you have a Windows 8 or above then you need to turn off secure boot and select boot from USB before using the thumb drive. The thumb drive boot will also allow you to check out the rest of the puter. It helps to have a thumb drive or a external drive hooked up when you boot so you can copy your data and files to.
If it has a CD/DVD you can burn Linux Mint ISO right to a CD and boot with it.
Once you got the bootable thumb drive created, insert it into one of the USB ports. Also plug in the medium you selected to copy your files to. Press the power button and start tapping the ESC key. This should bring up the boot menu. Select the USB thumb drive and it will boot to a menu asking if you want to start Linux Mint. Click on Mint and let the system boot. Find your hard drive and copy your files to your back up medium. If the hard drive is a SATA drive it will show as sda. If it has partitions then the first partition (C Drive) will show as sda1, the next partition will show as sda2 and so on. If you have 2 drives the next drive will show as sdbx. X being the partitions if it has any. Normally external drives show as sdd or sde. I have seen Linux recover data that people claimed could not be recovered. Keep in mind while looking for your files, and this is a Vista or above version of Windows, that you have to find your USER folder. The folder will look something like this. \Users\nameofuser\Documents. Repeat that for music, pictures, and videos.
Lets see if the hard drive can be made to boot again.Since the repair options are not working your best bet is to reset the lappy back to factory settings as if it just came out of the box. This will erase everything on the hard drive.
Post make and model and I'll post a more specific answer. Since you did not list the make and model, this is a generic answer. Some or all of it might help you.
Make sure you back up all your files before doing this.
If your resetting a lappy, make sure you have the AC adapter plugged up. You do not want this process interrupted. This should take one or two hours. It is best to check on it to make sure everything is going fine.
Recovery from the BIOS/UEFI. My preferred method. Since you try to upgrade M$ most likely deleted your recovery partition to prevent you from using it. But it is worth a try to find out. If it is deleted you will get an error when you try the info below.
When you press the power button start tapping the F key for your puter and the BIOS menu will open. Select recovery from the menu, answer the question and the recovery should begin. Depending on your puter this will take one to two hours.
Manufacturers BIOS menu F key
HP/Compaq ESC
ASUS Del
Sony F2
Samsung F4
Gateway, eMachines F10
Acer, Dell, Fijitsu, Gigabyte, Toshiba F12
Your BIOS menu should look something like this. Yours might be different. I am posting this to give you an idea of what it looks like.
ESC = BIOS menu
F1 = System Info
F2 = System Diagnostic
F9 = Boot Device options
F10 = BIOS Setup
F11 = System recovery