Code of radio?

I have a renault clio. After changing a fuse because of the radio not working, when I enter the code the previous user gave the radio only beeps. I can enter the code (with no beeping) but then whatever I press next it only beeps. I can't get it to accept it, is there a tip for that? Is it because the code is not correct? What should I do?

Thanks for the help
C

May 2008