If you can, i suggest you just try to reinstall it. There is no harm in doing so; the thing is already broken. try a different installer or installer method
Ive just had a similar problem i bricked my slim trying to make a pandora battery and a mms but i still already had one so thought i'm ok i'l just put it in and flash it back but it was sticking at format flash 1 so i had to make a different mms but kept the same battery and when i tried it stopped again at format flash 1 so i went into nand operations on the boot menu and format flash manually once i done this it flashed to 5.00 m33 straight away so maybe you need to do the same.
you could try installing a NAND dump from another slim PSP..but it's risky at best..if you do this..make sure you DON'T FLASH THE IDSTORAGE!!!!(this will definitely give you a bricked psp)
1. press x to downgrade using ms0:/UPDATE.PBP
2. press O to backup nand to ms0:/nand-dump.bin
3. press [] to restore nand from ms0:/nand-dump.bin
CHOOSE [] to restore the nand from the dump you got from the other slim psp will get this next screen(CHOOSE X...NOT L+R+start+select!!!!!!):
1. press X to restore nand without id storage.
2. L+R+start+select to restore nand with idstorage (only if dump is of your nand!)
also found this for you(from wasted420):
There is a bug in 3.71 M33-2, when using the 'Toggle Flash' options in recovery mode.
using it to write to flash may cause your PSP Flash Partition tables to become corrupted.
You will need to use NandTool to re-partition your PSP Flash memory.
Installing Nand-tool
(most users can skip this step as I've included Nand-tool as a part of the Pandora Install Files)
1. Download 'NandTool 0.3b1' and extract it to a folder on your computer, you will get a file called 'backup.elf'
2. Insert your 'Pandora Memory Stick' into your PSP and connect it to your computer (or use a memory stick card reader)
3. Copy the 'backup.elf' file and paste it inside the "KD" folder and overwrite the existing file.
4. Close the USB connection and disconnect the USB Cable. (or take memory stick out of the card reader)
Instructions on Using NAND-Tool:
5. Make sure you have at least 33mb of 'free space' on your memory stick' for a original PSP, or 66mb for a slim PSP.
6. Insert 'Pandora Memory Stick' into your PSP
7. Insert 'Pandora Battery' into your PSP while holding the 'L' button to access 'Pandora Recovery Menu'.
8. Hold the 'Square' button for 2 seconds to start the 'NAND Dumper' program.
9. On the next screen, press 'O' to go to the next part of the dumper.
10. Choose 'Dump from NAND' option and press 'X', choose "Nand-dump.bin' and press 'X'
* Please wait while your PSP NAND is being copied to your memory stick *
11. Once the dump is completed press 'X', now press 'O' to go back to the main menu.
12. Select the 'Other' menu option and press 'X'
13. Select the 'Repartition lflash' option and press 'X'
14. Press 'Triangle' to confirm you want to 'logically format the flash'
* Wait while the lflash area is logically formatted *
15. After the lflash format has been completed, press 'X'
16. Press 'O' to go back to the main menu.
17. Scroll down to 'Quit' and press 'X'
18. You will now be back at the 'Pandora Recovery Menu'
19. Press 'X' to install 'Custom firmware 3.71 M33' and it should install custom firmware.
After the custom firmware install has finished, your PSP should hopefully be working properly.
I recommend you to make another backup of your NAND using 'NandTool' and making a copy of it to your computer.
Overwrite the 'old non-working dump' with a new dump of your working PSP.
If the 'flash' gets corrupted again, you can restore the dump instead of repartitioning and installing the custom firmware again.
