Hmm, I'm pretty sure ESF has to be in the Half-Life directory, not the Counter-Strike dir.
Only time esf should be installed to the CS directory is if you are still using WON and the Retail CS cd like I used for WON. Since there's no "retail" version of anything for Steam (all apps are downloaded and installed thru the Steam client-- reason why you don't need a CD to install anything) you'll need to install Half-Life to port all your Mods to its engine.
Uninstall ESF from your CS directory first. Then if you don't play CS, uninstall that as well. Install HL instead. Then reinstall ESF to the HL folder.