Ok, let me try and make this easier:

If you choose to use 2.71 SE b2:
1. Create three folders:
(/iso)
(/psp/game271)
(/psp/game150)
You need all three. Any homebrew put in the (/psp/game) folder by default will be run as if on 2.71. (you can change this).
Any inside (/psp/game271) runs also like it is 2.71, any inside (/psp/game150) runs as if on 1.50.

To downgrade, you need to turn off your psp COMPLETELY (IE, either remove the battery or hold it untill it turns off.). Hold down the right sholder button as you start the psp, and you will get into the recovery menu.

Inside this recovery menu, you can downgrade to 1.50... If you deleted some stuff you need to do that, let me know and I will go look for it.

^_^ Hope that helps... If I messed anything up here, someone let me know.

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