My macbook is not letting me download skype google crome and other programs . how can i fix it ?

it always say application can not be open due to the version i have it on .. how do i change the version?|||If I had to take a guess, you have an older Macbook, from around 2006 or 2007. You're running Mac OS X 10.4 (Tiger). Most new programs use features that are only available in newer versions of Mac OS X: 10.5 (Leopard) and 10.6 (Snow Leopard). the only way to use those programs is to go out and buy a copy of Snow Leopard. It's only $30.