several errors related to Beamer

Hi,
I am quite new to Beamer and have faced the following errors while compiling a Tex file which somebody sent me.

Error: Encoding file `ly1enc.def' not found.
Encoding scheme `LY1' unknown.
LaTeX Error: File `marvosym.sty' not found.

I would appreciate if you would explain me how to fix these errors.
Thanks,