half life mod error

[leif16]

Heres the deal i realy want to play seven co opand other half life one mods but whenever i try to join a server after it loads it says:
Your .dll [cl_dlls/client.dll] differs from the servers.
what do i do to fix this problem

[Ad Bot]

[General Nick]

Reinstall.

Your files don't match the servers files.

[Dr.Block]

Wasn't there some kind of update installer you had to download?