Windows 10: Windows Defender is gone - Win 10

Had some trouble with a virus recently and thought I had got rid of it using Malwarebytes as defender couldn't delete it. It quarantined files that seemed to attempt to disable windows defender. Since they were quarantined I thought nothing of it and assumed everything was fine. The three files in question were as follows.

HKLM\Software\Microsoft\Security center|AntivirusDisablenotify

HKLM\Software\Microsoft\Security center|FirewallDisablenotify

HKLM\Software\Microsoft\Security center|UpdateDisablenotify


I've since deleted them completely but nothings changed. When I open Windows security, the box only says 'security at a glance' with the explanation below it, none of the tabs or settings for other stuff are there. When i go into the security providers by clicking the only settings button on the bottom of the mostly blank page, I cant click anything, antivirus, firewall and web protection are all just text floating at the top.
Something seems to have rendered it completely useless. How do I fix this and is there a way to reinstall it? Should i stay offline while i try to fix it to prevent data theft?

:)

 

Why did the startup window get cleared?

I didn't missed any step, the list was gone and gone , even after using lot of programs the programs were not listed in that list.

 

Windows 10 Defender - How to make it default to task bar?

Windows Defender Notification Area Icon - Hide or Show in Windows 10

 

Windows 10 Tweaks

Pressing “Windows+Pause Break” (it’s up there next to scroll lock) opens the “System” Window.

Windows 10: In the new version of Windows, Explorer has a section called Quick Access. This includes your frequent folders and recent files. Explorer defaults to opening this page when you open a new window. If you’d rather open the usual This PC, with links to your drives and library folders, follow these steps:

• Open a new Explorer window.
• Click View in the ribbon.
• Click Options.
• Under General, next to “Open File Explorer to:” choose “This PC.”
• Click OK

credit to Lifehacker.