The most important part of hacking a PSP is what version of the firmware you have installed. If it's above 3.03, you're fucked unless you can solder in a modchip.
If you have 3.03, you'll need an early copy of Grand Theft Auto: Liberty City Stories. If you need a copy, go to GameStop and ask to test it out before you buy it. The only sure way to know if it's the right version is if it has the 2.00 firmware update on it - after hackers found out how to use GTA to hack the PSP, Sony made Rockstar patch the hole.
For more detailed instructions, read the
first post on this thread on MaxConsole's forums.
Alternately, for $10 and a 2-liter of Mountain Dew, I can do it for you (downgrading only - I can't solder). If you throw in a few blank DVDs, I can burn you a few... backups. PM me if you're interested.
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WHERE'S THE BEEF