The wierd thing about this, is that "ESF_OPENBETA" should not come as an installer (.exe).
ESF 1.3 Open Beta releases come in archive files (.zip)
It seems that this installer you used is not good enough at finding where Steam is installed on your computer...
This would be a problem with how the installer was created, so you should ask whoever made the installer.
Since we don't even know what installer you are using, we can't really help much.