Just an Update from FatMSPatch for 4.01 M33.
Dark-AleX has release a quick follow-up to CFW 5.00 M33, which updates the fatmsmod patch since it soppted working due to some changes from Sony.
To install Fatmsmod Patch, follow these steps:

Download FATMSPatch for 5.00 M33 Rar file
Extract the Rar file then Copy the file fatmsmod.prx in the root of memory [...]

Another great release from Dark-Alex 2 days after the official version came out. All you need to do is download the 5.00 M33 Updater below and extract in your PSP Memory stick under PSP > GAMES , and Run the updater.
 
DOWNLOAD:

5.00 M33 UPDATE

 
Notable Changes in PSP 5.00 Firmware Version:

Direct PSN access. PSN stands for PlayStation Network. If [...]

This is just an update with the old post on PSP 3.90 M33 Custom Firmware Upgrade.
 
All you need to do is follow these simple steps:

Download Update File
 4.01m33-2 update 
 
Extract the contents of the file and put UPDATE folder in GAME Folder
 
Run the m33 updater in GAME, and wait for update to finish
Make sure you have at least [...]

This FATMSPatch is for custom firmware 4.01 M33 / M33-2. If you are still using the old custom firwmare version read my other post here: PSP Fatmspatch - Lag Fix
Why use FATMSPatch?The fastest recent firmware in terms of psp-memory card access is the 3.71. After 3.71, Sony removed/changed the fatmsmod in 3.80, 3.90 and 4.01.Dark-Alex made [...]

You must already have custom firmware installed on your PSP.
To check if you have CFW go to Settings » System Settings » System Information.
If you are installing any firmware past 3.60 M33 you MUST UPGRADE first to 3.52 M33, and then 3.52 M33-3 to be allowed to upgrade. The only way to bypass [...]