Instructions
Eject your memory card from your PSP.
Insert the SD card or memory stick into your computer.
Select "My Computer" and choose the appropriate drive associated with your memory card. A new window will open with all files available on the stick.
Highlight the items you wish to delete and right-click. Choose "Delete" from the options, and wait for the files to erase.
Remove the memory card safely from your computer. Return to your PSP, and more memory will be available to run Netflix.