sorry Ipost it in wrong thread. Here is my problem. I tried to upgrade to yosemite to day, but when I click on free upgrade red warning said "an error occurred ", after that I tried to click on download, I saw it in launch pad, but nothing happened. I couldn't find what kind of error causing this problem. Anyone has any idea causing this I really need help. Btw my Mac is MBP with Intel I 5, 4gig memory and 350 gig hard drive, and I bought it in 2011. Thank you.