book downloads

ive tried downloading some books on openings, and it's not letting me open the d/l's. is there a certain program that i need in order to open these d/l's?

Where are you downloading them from?  Are they zipped and you have to unzip them?  Are they pdf files (you need adobe reader).  Are they word documents (you can find a word viewer if you do not have Office Word)?  Are they dejavu files (another reader you need)?  And what books on openings are freely downloadable?  Most of the very old opening books are free on google books.  Some are reviewable only and cannot be downloaded.  What opening books are you looking for?  You can probably download pgn games with any opening you wish and study those games with any pgn viewer or chessbase lite.  Most opening books are obsolete by the time they come out and most chess pros keep up to date on latest openings with their databases and latest games published such as the games at The Week in Chess, or here in the downloads section.