Is this from an add-on or another program? Contact its support.

This means that the 7-zip archive application that is used to pack the Firefox installer isn't able to create a folder to extract its content.

Are you using the small stub or the full installer?

• https://www.mozilla.org/en-US/firefox/all/

Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

The error message appeared even before I had 7-zip installed on the computer. I only subsequently installed it to try to solve the problem.

ranp said

Error message of "7zip cannot create temp folder archive". Running administrator with full rights. Tried installing with full installer. Tried running as admin. Please help, thanks

So where are you getting your 7zip from?

Installing 7-zip won't solve this. This is about the Firefox installer that is packed with 7-zip self extracting code. When you install Firefox then the 7-zip stub needs to create a directory to extract all the files. For some reason it isn't possible to create this folder.

You can try to clear the TEMP folder to see if that has effect.

Did you try to boot the computer in Windows Safe Mode?

Safe Mode boot worked. Why does it only work in safe mode? Thanks!

It is possible that other software (e.g. security software) that is running on your computer is causing this problem and if you boot in Safe Mode then this software isn't running.