I've been sent some voice-over via e-mail as a wav file.
The only way I could burn this to disc was as a data CD however FCP3 does not recognise the file although it appears to be a QT file.
Any help please.

It might be an unusual form of .wav

Since you use FCP I take it you use a Mac.

Try opening the file in a basic audio editor (Audacity is free http://audacity.sourceforge.net) and then saving it in another format that FCP likes.