I have downloaded several fonts and when I click on the folder to install the font a box appears that says that the file doesnt exist or cant be opened. any suggestions? Marcelle was the last font that did that.

Which folder?

Look at the FAQ : http://www.dafont.com/faq.php
Install the police exactly as said in this FAQ.
If you have problems, explain IN DETAIL what you do EXACTLY to know what you do wrong.