The Firefox installer is a self extracting 7-ZIP archive. To be able to install Firefox the files in the archive need to be extracted to a temp folder in the Windows Temp (%TEMP%/%TMP%) folder location. This error means that the 7-ZIP stub extractor isn't able to create a temp folder to extract the files. It could that security software or your IT department is blocking 7-ZIP archives. ----- Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems. *https://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/ *[https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10/]