I’ve found myself wanting to make screenshots on a PSP running CFW, (M33-6), several times recently. So I went ahead and extracted screenshotbmp.prx to the seplugins folder on my memory stick. Then I loaded up text edit and opened the game.txt and vsh.txt and added this line:
After that it was a simple matter of heading into the recovery menu to enable the plugin and now I can save bitmap images of the screen on the device. They are saved to the /Picture folder on the memory stick.