Before it got to the question it listed: File C:\users\Herman\Desktop\Games\DosBox\DosBox-o.63-install.exe|>$INSTDIR\dosbox.exe Error 42145 {Installer archive is corrupted.}
This is just a scan error message
win32:Dropper-gen [Drp] ,
This is a real infection

If you want a check, follow instructions and attach Malwarebytes and OTL logs http://forum.avast.com/index.php?topic=53253.0