If you have a 2.71 use the following:
For TA-082 Motherboard PSP:
[GUIDE] Downgrading a TA-082 2.71 PSP to 3.03 OE-A/B
Non-TA-082 Motherboard PSP:
[Tutorial] How to downgrade your Non-TA082 2.71 PSP to 1.50
To tell if you have a TA-082 motherboard on your PSP or not, look at the tutorials.
