But first we need to make sure that your PSP satisfies the basic requirements.
Then after a few minutes (you might just see a black screen again) the upgrade will be completed, and you will have to press the X key again to shutdown your PSP.
Now you have the 3.52 firmware, but you still have to apply the M33-4 patch.
This patch will fix any bugs since the original release, and it will introduce a few more features.
The procedure to apply this patch is quite simple; just navigate into the applications menu and run the app called M33Update #4.
If you're on offcial 3.71 firmware, the first step is to downgrade to 1.50. From here you can update to 3.71 M33 then to 3.71 M33-2. The kernel addon will allow the execution of homebrew designed for firmware 1.50. For both Fat and Slim: This procedure should work for both Fat and Slim PSP's. It can unbrick or upgrade a PSP straight to 3.71 M33-2. After Installation, Install the 1.50 kernel addon if you have a Fat PSP.