I set out to upgrade my iPhone software yesterday. After buying the phone, I followed Alex's instructions for cancelling my AT&T service, so now it's an iPod Touch with a SIM card slot. I've been using the iPhone as a testing platform. I have not performed any of the hacks against it.
So, I thought the upgrade would be a breeze. I was wrong.
After connecting my phone to iTunes on Windows XP, iTunes prompted me to upgrade. It downloaded the new software and applied it to my phone. Somewhere in the process (I wasn't really paying attention), I received the infamous yellow triangle of death. The instructions on how to fix this are after the jump.