Hi, I have a iMac 27 , Mid 2010. Right now, it has 2GB x 4 slots = Total 8GB installed. I wanted to make it 16GB, so got 2 8GB kits from Crucial, http://www.amazon.com/Crucial-PC3-12800-204-Pin-Modules-CT2C8G3S160BM/dp/B008LTBJFW/ Then just took out all of my 2GB RAMs and placed in 2 8GB in two slots. Kept other 2 slots vacant. Now when I start, the iMac gets to the desktop screen , and then restarts . Whats going on ?