You have to run half-life before installnig esf. Just run half-life and when you get to the menu exit half-life. If it is the first time you have run half-life on this install of steam, enter the hl training room and run around for 10seconds and then exit before installing esf.
Earth Special Forces will only work for Half-Life 1 & Counter-Strike v1.6. So the modification will not work on any other games then those. This includes Half-Life 2, Half-Life: Source, Counter-Strike Source, and Counter-Strike: Condition Zero.
Earth Special Forces Will Work With -Half-Life 1
-Half-Life 1 Anthology
-Valve Complete Pack
Earth Special Forces Will Not Work With -Half-Life 2
-Source Premier Pack (includes Half-Life: Source)
-Counter-Strike 1 Anthology