My friend Arnold just posted this on his site VSH Volume Remap
VSH Volume Remap By ArnoldBronson
What is does is remap the volume buttons onto the dpad up and down so that you cna change the volume of the PSP.
This is so that people who have non-functioning volme buttons can still change their volumes.
It's a VSH plugin with toggle, therefore you can change back and forth easily to change the volume. :)
For more info, go to: Arnold's Site