Yeah I did that to my psp..had some nintendo roms and some game iso's (iso loader)
It was cool, but I played Socom online so I had to revert back to a "good" firmware.
Sorry for being vague (i'm pissed off right now), if you need more help pm me.
Well i successfully modded my psp. I was at v2.71, then upgraded to 2.8, then downgraded to 1.5 not I'm running DA 3.40 OE-A. Now I'm running at the full 333mhz and now I just got to to find some iso's.