Earlier today I dual booted Manjaro KDE and Windows 10 on my laptop however whenever I turn on my computer and select to boot to Windows my laptop attempts a start up repair which fails and proceeds to either give me the blue screen of death or give me another blue screen with troubleshoot options (none of which work). What can I do to save windows or must I factory reset it?
For questions how to save Windows, as @c00ter said, ask Microsoft.
However as to figure out what happened so it doesn't happen again next time you install a dual boot: Looks to me like you failed when making room for Manjaro. Either the shrinking of the windows partition failed, or you managed to change something that Windows needs to work, like changing the UID for the Windows partition which of course makes the Windows boot manager fail.
Again, please ask Microsoft regarding Windows issues, but keep those things in mind for next time.
You should have backed up Windows. If you don't find a better solution you can reinstall Windows. And you will need a Manjaro live USB again to chroot into Manjaro and reinstall and update Grub, so you can boot to Manjaro again.
It was my pleasure to move this from technical questions to other operating systems
Since your main problem seems to be with the Windows Boot Manager, I'll leave you some links that may help you get to a solution, but from what you've described you may have to just re-install everything.
Best of luck. Microsoft also has a forum if you would like to talk with them about this!
@ThomasV I just remembered something extremely important. When you resized your partitions did you do it from the Calamares installer (aka the Manjaro installer) or using the Windows disk mananger? If you modify your C drive using any external software then Windows will assume that corruption has occurred and keep attempting repairs. This is because Windows is still trying to load into the space where Manjaro currently is. It's a Windows thing. It assumes it own the entire drive unless you tell it not to.
If this is the case, try the steps in my earlier reply, and on the MS forum mention that you reduced your C drive from an external Linux installer and you need to get Windows to stop attempting repairs.
Alright. This will be my last reply. Sorry for the confusion and 2nd post but i felt this was too important not to mention.