This  installer includes everything you need to install Signed 5.03 kxploit v7 + 5.03 Prometheus-4.
http://www.mediafire.com/?t4m7akbj4gfamqy

Just select your PSPDrive and install it.

You must upgrade by that way:
*to install chickHEN,you must have OFW 5.03 installed
*launch chickHEN (go to your PICTURES and scroll very fast down)
*.:: PSP "Crash" ::. (if not try it again and again...)
*chickHEN is installed
*install CFWEnabler under Games » MS » CFWEnabler
*Turn off your PSP (FULL SHUTDOWN)
*launch 5.03 kxploit under Games » MS » 503kxploit
*install 5.03 GEN-C under Games » MS » GEN-C Updater
*PSP Restart » GEN-C is installed
*install 5.03 Prometheus under Games » MS » 5.03 Prometheus Updater

If you turn off your PSP (FULL SHUTDOWN) you need to launch 503kxploit and you're again on 5.03 Prometheus-4

Statutory Warning: I’m not responsible if you brick your PSP following these steps.

Proceed at your own risk!!!

I tried several times and there was NO brick!

-flofrucht