Windows 8.1: Slow Unresponsive after Updates 29 April 2016.

Mine was caused by Windows Defender / Health Check - Lets kill it.

Log in to Safe Mode.

Option 1:
Enter from sidebar - Setting > Change PC Settings > Update & Recovery > Recovery > Advanced Startup | Restart Now

Takes sometimes to restart. Select Advance Option > Restart Option > Safe mode with networking.

Option 2:
Windows Key + r > type: msconfig & click OK > Under Boot tab > Tick Safe Mode & Network > Apply & OK

Tell Windows to restart and wait.. Your PC are lot faster & responsive in safe mode. In safe mode:

Windows key + r > type: regedit > Look for:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender
Change the value of:

• DisableAntiSpyware 0
• DisableAntiVirus 0

Close the Window.

If you choose Option 2, you have to reset msconfig by unticking safemode. To get back to msconfig, follow Option 2.

Close the Window, try restart normally & pray. If it does not work, go back to safe mode.

1. Go to uninstall updates
2. uninstall all updates dated 29 April 2016.
3. Then, restart. Takes sometime.
4. Window will tell you that uninstall failed and will automatically restart - let it be.

By now, your computer should be working normally. Looking at Event Viewer,
There are bunch of:
"The device, \Device\Harddisk0\DR0, has a bad block." errors &
"The IO operation at logical block address 0x1970 for Disk 0 (PDO name: \Device\00000001) was retried." errors

Updated Windows Defender were built for Windows 10 & blindly (purposely?) installing itself without considering Windows 8.1 (In another words MS are forcing you to upgrade to 10)

..that may include ONLINE health/disk check? Why? All our files need to be uploaded for checking?

Nude again..

UPDATE: 4 May 2016.
Manage to download install Avira. Took around 1000 years to install. Those installer around 5MB. While installing, downloads took around another 300MB.
Avast cannot be installed anymore due to bla.. bla.. bla.. _av_iup.tm bla.. bla bla code 0x2 stub error.