We are M$. Resistance is futile. Your puters and lappies will adapt to service us. We will add your technology to our own. M$ has announced that Windows is NOT a top priority. Pushing people to use the cloud and mobile has become their main focus now. The truth about 10 is coming out.
As you have found out, M$ is willing to do anything to get the market share of 10 to increase. They make the promise that you can go back if you don't like it. Then the install fails making it so you are stuck with 10. They also deleted your recovery partition so you could not use it to do a clean install of the original OS. To them, stealing your privacy is more important then your right to choose which OS you want.
Since it will not boot you will have to create a install/repair thumb drive with the link below. This will allow you to try to repair 10 first and if that does not work do a fresh install. If you have to do a fresh install make sure you have a good product key and all the drivers before starting a fresh install.
https://www.microsoft.com/en-us/software-download/windows10
Once you get the thumb drive made then you can boot from it. When it boots, select your language preferences, and click next. When the next window comes up look to the bottom left hand corner and select repair my computer and then select troubleshoot. Keep in mind that there is a good chance that if you get 10 repaired you will lose the go back feature and be stuck with 10
http://www.tenforums.com/tutorials/4588-system-restore-windows-10-a.html
http://www.tenforums.com/tutorials/4130-reset-windows-10-a.html
Hopefully you can get it to boot to the desktop and the go back feature is still intact allowing you to restore your original OS. Going back to your original OS is your best bet. Windows 10 is a nightmare of an OS that is going to get worse as time goes by. Between the forced updates to the built in back door you will have no idea what is happening to your puter.
If it has been less then 30 days try this. Back up everything important and then try clicking Start, Settings, Update & security, Recovery, Go back to (last version).
You wont be able to use the recovery partition since M$ downgraded you to 10. M$ deletes it to keep you from going back. It is my opinion that M$ deletes the recovery partition to keep people from going back to their old OS. I guess if you write as many bad OSes as they do you got to find a way to make it look like everyone likes it. If the go back is missing then you will need to order the recovery DVD's from the manufacturer. Some manufactures still have recovery DVD. Post your make and model and I'll see if they are available.
If you had Windows 8.1 you can use the link below to go back. You need to back up everything up and make sure you have a good product key on the bottom of the lappy. I do suggest that you download all your drivers before attempting this.
http://windows.microsoft.com/en-us/windows-8/create-reset-refresh-media
If you had Windows 7 then you will have to jump thru some hoops but it can be done. You will have to buy a 7 install DVD. We have had a lot of success so far getting people back to 7 if you are willing to do the work. No guarantees.
http://www.newegg.com/Product/Product.aspx?Item=N82E16832416804
When buying from Amazon make sure they have a high customer rating. DO NOT buy from the new comers.
https://www.amazon.com/s?ie=UTF8&page=1&rh=i%3Aaps%2Ck%3Awindows%207%20professional
Make sure when you go back that you DO NOT let these updates in. M$ is now hard coding spyware (back door) into Windows 7 and 8. Go to the control panel and click on Windows updates. In the upper left corner click on change settings. Then change important updates to never check for updates. This puts your updates in the manual mode. Reboot the system and go back to your control panel. Click on Windows updates and then click check for updates. Find the update KB 3035583 and hide it so it does not get installed again. Let us know if this does not work, M$ keeps coming up with new methods to force 10 on people.
You should also hide these updates KB 3068708 KB 3022345 KB 3075249 KB 3080149 These updates give 7 and 8 the same spying capability as 10 has.
You should also hide these updates KB 2952664 KB 2976978 KB 2977759 KB 3050265 KB 3050267 KB 3068708 These have to do with compatibility with being upgraded to 10 and need to be dealt with."