Q: Windows Defender: 0x80070424 error

Windows defender will not start. When attempting to activate, the "0x80070424" error code appears. Recently removed a virus that must have deactivated the program, but now cannot start back up.



Q: When you were running Vista, had the preinstalled Norton free-trial already expired by the time you installed Avira AntiVir?
A: The trial had expired before I installed Avira

The computer is still infected & chances are it's been infected for quite some time...especially since the Norton free-trial had already expired by the time you install AntiVir and since you didn't run the Norton removal tool before you installed AntiVir.

OPTION A: Microsoft PCSafety provides home users (only) with no-charge support in dealing with malware infections such as viruses, spyware (including unwanted software), and adware.

[This support is also available via the Consumer Security Support home page:]


1. See if you can download/run the MSRT manually:

NB: Run the FULL scan, not the QUICK scan!  You may need to download the MSRT on a non-infected machine, then transfer MRT.EXE to the infected machine and rename it to SCAN.EXE before running it.

NB: Make sure you download the 64-bit version of the MSRT!

2. Now begin your own, new thread in one (only) of the following recommended forums for assistance by an expert in such matters.  DO NOT SKIP THIS STEP!!

   • SpywareHammer: Malware Removal

   • Spyware Warrior: Help with spyware removal

   • DSL Reports: Security Cleanup

   • Bluetack: Malware Removal

   • MalwareBytes' Anti-Malware

...or the forum where you posted before you posted here.

OPTION B: See...

   • Cleaning a Compromised System

See the ANSWER post in this thread and follow those instructions (to-the-letter and in order!) to return your computer to a secure & functional state.

Wish I'd had better news for you. Good luck!

~Robear Dyer (PA Bear)
Microsoft MVP (Windows Client) since October 2002

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Views: 20,351 Last updated: July 4, 2018 Applies to: