e-mail problems

I hope that this is the right place to post this, and I apologize if it is a repeat, I could not find an answer in search. When I get mail from my friends and it has an attachment that is a video or wav, and I try to open it , all I get is a bunch of gobbledygook letters. I'm a switcher, so forgive me if this is just a basic fix, but I can't seem to open any attachments. The body of the mail is fine.

Thanks

Scott