first of all, what kind of computer do you have. I had the same problem on my computer with counter strike and esf. It might not sound important but your computers ram and stuff might not meet up to the needs of the game. Here are some tips i can think of for you.
1. try reinstalling half-life and esf.
2. test it on another computer if possible.
3. re-download esf and install it again.
4. make sure your computer meets up to half-lifes requirments.
5. if you didnt buy your half life copy and you downloaded off the internet instead, it wont work. go buy half life and install it.
6. Update half-life to version 1.1.1.0. you can download the update tool from
here . If that doesnt work just google "half-life 1.1.1.0." and some web sites will show up
All of that stuff should work for you, I got esf working on a windows 98 with a 16 megabyte graphics card. If you need any help just email me at
[email protected].