Suggestion to Dylan Bennett / Chimera 1.8rc 64-bit as Default Application Hi Dylan, you asked how to get Windows 7 to acknowledge Chimera as the default program to open specific files. In my experience the same problem was solved by running Ccleaner up to 3 times in a row to fix registry keys. After the first run, re-scanning the registry with Ccleaner shows that .pdb entries still need to be fixed. I kept running Ccleaner on my computer's registry until it was deemed as clean and only then was file association successful. Hope this helps, Antoine