Instructions
Remove the battery and memory stick from the PSP. Insert the Magic memory stick into the PSP card reader.
Insert the Pandora battery. Hold the "L" trigger on the PSP and turn on the PSP. The PSP is now in service mode and you will see the Pandora menu.
Select "Install CFW" from the Pandora menu. Select "Yes" to verify your selection and your PSP Slim will be unbricked.
Press the "X" button to shut down the PSP. Remove the Pandora battery and Magic memory stick. Reinsert the normal ones that were removed in Step 1. Turn your PSP Slim back on and it should now be working.