First you will need to download the files needed:

- Custom firmware installer 3.03 OE-C
- Official Sony firmware updater 1.5
- Official Sony firmware updater 3.03

Now follow this guide:

1, Extract the custom installer archive into a directory on your PC. Format your PSP memory stick and then copy the oeupdmaker and oeupdmaker% directories from the 303OEC archive into the /PSP/GAME directory on your PSP.

2, Extract each of the firmware 1.5 and firmware 3.03 files and rename them to 150.PBP and 303.PBP respectively. Then copy them both into the oeupdmaker directory on the PSP memory stick.

3, On the PSP, make sure the battery is 100% charged and plugged into the mains.

4, Run the program "oeupdatemaker" on you PSP and don't touch anything. Just wait for it to finish. This will generate a special data.dxar file that combines the best bits from both the 1.5 and 3.03 firmwares.

5, Once this has finished, now you can copy the 303oeflasher and 303oeflasher% directories from the custom installer archive to your PSP in the directory /PSP/GAME

6, Finally copy the DATA.DXAR file that was just created on the menory stick into the 303oeflasher directory on the memory stick.

7, Now make sure your PSP battery is still at 100% and the mains are connected and you are ready for the final step, the actual upgrade.

8, Finally run the 3.03 OE-C flasher program on the PSP and wait for it to finish. Following the on-screen instructions.

If all goes well you are now running a 3.03 OE-C PSP.

Please let me know if you have any further questions.