Based on the book Hacking the PSP, Extremetech has published a guide on running Linux and Windows on PSP.

So the PSP can do games, movies, video, music, photos, and Internet. Well, that’s not enough—it should be able to run software we enjoy on our home PCs! Utilizing an open source x86 emulator called Bochs, which emulates the hardware usually found in PCs, and creating a few hard disk images with the software we want on them, you can run Linux and even Windows on your PSP!