help please

look i got the game half life today i installed the game and it works fine. now when i try to install the esf mod it does everything right but when its going to install it say the file c/ programsfile/halflife/hl.exe/esf/autoexec.cfg could not be opened. please check your disk is not full and that you have access to the destination folder. the system could not find the path specifed. what do i do to fix this problem ?

Play HL once.

i did i even saved the game and it still does not work