From what you've explained, there is something on that disk that messed up your hard drive.
Before you go pulling everything out, open up your Amiga and disconnect your Hard Drive cable. This is the easiest thing to check first compared to removing chips and those dang accelerator boards that are a @#*& to install/remove...
As for the early startup menu, I don't know if the CTRL-A-A keyboard method will work instead of the mouse buttons. Try starting it up again with BOTH mouse buttons pressed down BEFORE you power up.
The hardest card to remove is the DKB 1240!!! DAMN that is a :griping::griping::griping::griping: to remove and install!! I would rather open the Amiga 1200 desktop all up and do changes there then remove that :furious: card. The Blizzard series are much easier to remove and install for some reason.
