I don't think there's much you can do, but I do have one idea. Get a UMD that needs a firmware between 1.51 and 2.71, and it should tell you that you need to update, and may run the updater. Had you been on 3.02 OE, it would just be a matter of going into Recovery mode.

But may this be a lesson to everyone else - 3.02 OE could save your PSP.

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