few days ago my powerbook started showing a screen at the startup, with a picture of on/off button half-transparent and some writings in different languages telling me that I should restart my computer.. after investigating what may have caused the problem, I realised that the problem started after I installed my airport ext. card and so it is not working properly and causing that problem in the OS. so I just took off the card and my PB started working without crashing.. I asked a long-time-mac-user friend about the problem, and he said it's called "kernel panic" and usually happens when the computer has a hardware problem. So, I just want to learn more about this "kernel panic" thing? could my powerbook be made fault just from the beginning or is it about the airport ext. card? what generally causes the kernel panic?