The one and only hack for you would be:
- Update to 5.03
- Install and run ChickHEN.
- Install and enable 5.03 GEN-B
This movie shows installing of ChickHEN and 5.03 GEN-B:
http://www.youtube.com/watch?v=DF4gNk2sPjw
Ill explain in short what should be done and why.
You first update to official firmware: 5.03
This because the update contains an error which can be exploited.
Then you put on the ChickHEN files and enable it.
This because now your PSP is allowed to run homebrew apps. (Such as 5.03 GEN-B)
Once ChickHEN runs install and enable 5.03 GEN-B.
This is needed as ChickHEN only supports running of homebrew and not ISO.
5.03 GEN-B does.
If you get stuck anywhere feel free to ask.
I highly suggest you read the sticky posts as they contain usefull info!