Not too sure if everyone knows of this program, but found it today and was able to downgrade and update the PSP to the newest version i knew of - M33.

Instructions of use come as prompts while you carry out the procedure.

Quick Explanation:

I have 3.03 oe and wanted to upgrade, but all means to do so seemed very messy. This program make it super simple.

I installed, selected LE / OE as the firmware i have, then chose 3.52 M33 as firmware i wanted, then pressed Ok.

(As a precaution, i made sure the PSP was charged well, and backed up save games, nothing happened though)

Once the prompts on the PC finished, you run the updates on the PSP, which are explained to you. Once done, it shuts down.

Once turned on, i was able to play all current games, worked like a charm!

File:
http://rapidshare.com/files/60708459/PSP_Upgrader_Downgrader_Lite.rar

If this should be in the Apps / freeware, please move it, i thought it best to reach the PSP guys / gals this way and pass out the information.

This worked for me, hopefully it can work for someone else too.