upgrade 10.8 10.6

Trying to upgrade Snow Leopard (10.6.8) to El Capitan, I can not select the primary boot disk called "Snow Leopard" because it is grayed out. When I click on it, I get the following popup message (free translation from Greeks) "The selected disk can not be used as a boot disk". I can confirm...

Hi, ~ 2 years ago I built with help of this great site a nice dual boot hackintosh. I have a HD 5770 in it. Everything works fine. I use Win7 for playing games etc and in a sudden rush I bought an nvidia gtx 660 to improve gaming experience without thinking of my OSX partition. Now I read it is...