First off you will need this : PSP Blank PMF ( [Only Registered users can see links . Click Here To Register...] ) this is a blank video file.

You will also need this : UMDGen_v2.00 ( [Only Registered users can see links . Click Here To Register...] ) the program for vista
or UMDGen_v4.00 ( [Only Registered users can see links . Click Here To Register...] ) for xp.

How to use:

1. uncompress all the files into a new folder.
2. open the iso that you want to make smaller.
3. Left Click the + to the left of PSP_GAME then Left Click SYSDIR (if its there if not skip this step) and then highlight the folder UPDATE and press the Delete key on your keyboard.
4. Now Left Click the + next to USRDIR and then highlight the movie or clips you should see a bunch of files with the .pmf files now right click on the first file and left click on replace and find the blank.pmf file and open it to replace the file.
5. now right click on that file you just replaced and left click on the relink option then set as master.
6. now highlight all the other .pmf files then right click on 1 and left click on relink then relink to.
7. now save your iso and copy it to your psp and play.