Works fine with me to.
IDEAS TO HELP YA:-
1. Go to windows update site and download all updates. - If that dont work move down the list.
2. Reinstall ESF - If that dont work move down the list.
3. Update Half-Life Then Reinstall ESF - If that dont work move down the list.
4. Reinstall Half-Life Then update it then Reinstall ESF - If that dont work move down the list.
5. format C: (only joking)
BrunO