Why won't my psp install Prometheus?

I have a PSP1001 (phat) running 5.00 M33-6 and want to add Prometheus 4 to it, but every time i install it, it doesn't work. I downloaded the right version of it and everything, and when i run it on the psp it goes through the installation process then says "Press X to run cfw" or something like that, i do and it reboots. I go to system info and it still says I just have 5.00 M33-6...What is happening?