I'm going to note that repair isn't simple. If you don't have a lot of free space on the drive, correct that.
If it's not that, read http://www.tomshardware.com/forum/id-3025528/windows-fatal-error-c00000d4.html
You have a lot of work ahead of you.
Issue: Computer has 2 windows 10 operating systems installed onto 2 different hard drives. I have set the PC to boot from the second OS (on an SSD) for faster boot times but this will not install updates. Everytime it gets to 19% then stops saying: fatal error c00000d4 applying update operation. How can I solve this?
Long Version: I have recently built a new PC with a decent spec from scratch. Originally an older version of windows was loaded onto my 1 TB (not an SSD!) hard drive. This was then updated to Windows 10. I proceeded to use this computer for a couple of weeks (including paying and installing a non-steam version of GTA 5). The start up time of the PC was slow so a friend recommended buying a cheap SSD and installing the OS onto there to improve start up time.
Being a computer newbie I had no idea how to do this whilst keeping all my files so instead (as I had a spare licence of windows 10) decided to install another version of windows on to the SSD and boot from there. This seemed to work although I 'lost' (couldn't access?) all of the files I had on the previous hard drive (RIP GTA 5).
I have been using this computer for about 2 months when I noticed the computer could not install updates. I tried running the windows update troubleshooter - it found no issues. I tried running the system file checker on the command prompt (sfc / scannow), this found some corrupted files which it then fixed but the computer will still not update. Finally I downloaded CC Cleaner and did a registry clean but still not luck with updating.
I think the issue might be to do with having the two operating systems on the same PC - what's my best bet to solve this? Delete my old OS perhaps? Does anyone know of an idiot-proof program that can do this?
The Computer Idiot