Thank you The error is now fixed, however the registry entry doesn't get added, if the line is used in a shell it gives this output: WindowsXP C:\Documents and Settings\Administrator>REG ADD HKLM\\Software\\Microsoft\\Windows\\CurrentVersion\\Run /f /v Whileidle /d \"\\\"%APPDATA%\\WhileIdle\\WhileIdle.exe\\\"\ Error: Too many command-line parameters Windows 7: C:\Users\Administrator>REG ADD HKLM\\Software\\Microsoft\\Windows\\CurrentVersion\\Run /f /v Whileidle /d \"\\\"%APPDATA%\\WhileIdle\\WhileIdle.exe\\\"\" ERROR: Invalid key name. Type "REG ADD /?" for usage. My guess is that it's not supposed to work being interpreted by a standard Windows shell and only 7-Zip SFX interprets it correctly? The program installs and triggers to execute, however, the registry entry isn't added.