You can download a simple program that will do it quite easily for free,I use a program called switch which I got by googling "wav to MP3 for free".When using this program you have the choice to either overite the original or to save as another file in mp3 format.You will find that there are lots of programs to choose from .
thanks marti ill give it a go.... I have tried a couple of converters
but either lose the files somewhere in comp or rip wav onto converter then cant convert to mp3....anyways fingers crossed