I have an early 2006 mbp. I was rendering an after effects project (as i do most days) and the machine shut down. Now it wont get past the gray screen with the spinning circle when trying to boot. I was able to install the os onto an external drive, then migrate all my files onto that so everything is backed up. I am using the computer now but have to boot from my external backup. Already tried re-installing snow leopard but got errors 3 times saying it cant install. I still can access my HD when booting from the external. Disk Utility says nothing is wrong. Any ideas?