Apple has an OS Upgrade for all Apple Computers Manufactured from 2007 or 2008!
You can upgrade to OS X El Capitan from OS X Snow Leopard or later on any of the following Mac models. Your Mac also needs at least 2GB of memory and 8.8GB of available storage space.
MacBook introduced in late 2008 or later
MacBook Air introduced in late 2008 or later
MacBook Pro introduced in mid 2007 or later
Mac mini introduced in early 2009 or later
iMac introduced in mid 2007 or later
Mac Pro introduced in early 2008 or later
Xserve models introduced in early 2009