installer manifest failed signature validation
To remedy the situation with updates turned off you will need to get some up-to-date certificates: and follow part of the great instructions of a random internet comment by MIKI:
Skip this:Do this using the attached file:The certutil.exe tool need to be upgraded to use new commands, to do so you have to install the KB2813430 update:
https://support.microsoft.com/en-us/hel ... -trusted-a
Once you do this your certutil.exe file is updated and you can use the -GenerateSSTFromWU command.
Then go to the dos window (cmd) and type command “certutil.exe -generateSSTFromWU x:\roots.sst” where x is the drive where you want the file sst to be created.
The operation need 1-2 minutes, after the file is created load the MMC console.start->run-> MMC -> add snap-in -> certificates -> computer account > local computer>press ok->press ok.
Then expand Certificates->Trusted root certification authorities-> certificates, right click on certificates -> all tasks -> import, choose the SST file created before(set file type to .sst), press the browse button and choose Trusted root certification authority from the list->do not save console1 changes.