Placasoft has released PSPset for the PSP. This tool changes booting to games on the PSP, because it writes to the flash it comes with a massive warning, heres what they say:
"Copy the gameboot.pmf on the root of the memory stick. (ms0:/gameboot.pmf)
Attention, the Gameboot.pmf file shouldn't be much larger then 1MB.
I'm not responsible if you damage your PSP. Try it at your OWN risk!