also von der dvd in steam installiert/integriert?!
wenn ja:
starte es mal über steam!!
wenn nein:
versuch mal deinstall und reinstall... und nich über dvd starten sondern über steam (soweit ich weiss!!) bei mir ist das so... kann es nicht anders starten!!
“Please install Half-life 2 Retail Standard before continuing. Installation of Half-life 2 Retail Standard is required before continuing. Please insert your Half-life 2 Retail Standard CD/DVD into the drive and select ‘install’ from the autorun menu.”
Answer
If you are still encountering this error please exit Steam, open the Steam folder on your hard drive (the default location is C:\Valve\Steam) and delete the ClientRegistry.Blob.
Once this file has been deleted restart Steam. After a short update you should be able to log in and play