well, can't give any guarantees, but this is what i would do ...

firstly, end all other applications running and try just running the gnutella client.

if it doesn't work and you get the same error message, i would simple move (rename) the dll and then install a client again. maybe this puts a suitable version in place. if i couldn't get it to run this way, i might make a clean install of windows and try again.

maybe this helps you on. good luck - you will succeed after all btw, next time tell us what version of win you are running.