Dear users, I've come to this forum for many problems that I had over the last years with my iPhone, iPads and macbooks. But now I cannot find the solution to my problem. So I am hoping I can find it in this thread. The issue is as following; I've upgraded my macbook (2010 bought) to Yosesmite and it became terrible slow. So after using it for a while I decided to downgrade it to Maverick. Also when I tried to clean my laptop the first time I got the error that it couldn't delete a partition from the harddrive because it couldn't be deactived. So that issue also stands. Don't know if it's related to the problem. I plugged in my USB with Snow Leopard to install it on the harddrive but everytime I select the usb in the boot menu I get the following error on my mac; . Things I have tried so far; Wiping my whole drive clean and then trying to install it; No luck. I wiped the whole harddrive clean and then reinstalled Yosesmite, because I was able to do that.. I really wanna downgrade to an earlier version. But this error keeps occuring. I hope my story is clear enough to get some help. So yeah.. Anyone got a bright idea?