when your flashing the bios of ur psp(installing CFW), and remove the battery, your psp will be bricked. you can tell because when you turn it on, it wont show anything but a black screen.
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There is nothing either good or bad.
But thinking makes it so.
Be sure to make backups of your PSP files just incase and flash0 files I semi bricked my PSP numerous times messing with flash 0 files.But be warned you can also get a full brick from editing flash 0 files if you want fancy themes I think you should use the CXMB plugin istead of flash 0 files.