If you’re looking for the required files to install custom firmware on your PSP look no further. Both 500.pbp and 550.pbp are used to update your PSP to their respective Sony Firmware, 5.00 for 500.pbp and 5.50 for 550.pbp.

The PBP file for 5.00 M33 and 5.50 GEN-D3 are linked below:

500.pbp for 5.00 M33.
550.pbp for 5.50 GEN-D3.

If you’re wondering what those files are for, please check out how to install custom firmware on your psp.