pfw

Im trying to downgrade my PSP 2000 to a OFW between 2.60 to 3.52 so I can upgrade to 5.00 M33-6 but I always run into an update problem. My PSP states "The update cannot be started. The data is corrupted" when I try to install an update before 5.00 OFW. I was able to get on 5.00 OFW but thats...