Unable to open SteamNew.exe for writing

This error is related to security software, spyware, or a virus preventing the SteamNew.exe file from being written over the course of the Steam.exe update process.

1. Check your security software's settings
   If you are running an antivirus program, firewall program, or any security product which may be interfering with the deletion and replacement of the Steam.exe file (some security software will check a file's information every time it is changed and block automatic replacement of files) please check your settings for the program and make sure that you are prompted to allow activities which may trigger the security software.
2. Disable any programs which interfere with Steam
   Please consult the Programs Which Interfere with Steam topic to ensure any programs on the list are either disabled or uninstalled.
3. Remove Spyware, Adware, and Viruses
   If the issue persists it is possible that a virus, adware, or spyware may be interfering with the installation process. Please see the Spyware, Adware, and Viruses Interfering with Steam topic for instructions to remove the offending program.