Instructions
Turn the PSP off.
Connect the PSP to your computer using the proprietary USB cable. Turn the PSP on.
Set the PSP to "USB Mode" by going to the "Home" menu, scrolling all the way down, and selecting "USB Mode." Your computer will bring up a folder displaying the contents of your PSP. Double click the folder.
Select the "Video" folder.
Drag and drop the video files you want to move to the PSP. The PSP is compatible with MPEG-4 (aka MP4) and AVI video formats.
Use the directional pad on the PSP to scroll over to the "Videos" menu. All video files can be found here.