Welcome to the forums, this thread belongs in the Help section since your problem isn't technically a bug.
So without further ado, moved to help...
And as for your problem - first try disabling voice through Customize -> Advaned Options (I'll presume you are using WON and not steam..). If that doesn't work, just reinstall the latest version of ESF, that should give you the required file which is missing (voicecon.spr).
(As a side note, it would also be a good idea to make sure your version of Half-Life is updated to 1.1.1.0)