Reinstall the Source SDK installation/en
If all else fails, it may be necessary to re-install the SDK tools. It is advisable that you make a copy of your entire
"..\SteamApps\username\sourcesdk" directory before following this procedure. After you've reinstalled the SDK, you have a backup in case there is some content in your sourcesdk directory that you may wish to restore.
- Shutdown Steam by choosing Exit from the Steam task bar icon menu.
- Delete the
"<Steam Install Directory>\SteamApps\username\sourcesdk"directory, where the SDK resides.
- Delete the sourcesdk.gcf file from the
- Restart Steam and launch the SDK application.
Steam will automatically re-install all the necessary files.