I am gonna give and show you how to install the presell guns and costumes. First off if you use cfw you will have to go to ofw to use this then go back to cfw. Sorry about your luck !!

First download these files:
Code:
megaupload.com 6M8IE8KB
After extraction you will have a folder called Presell Addons inside, two more folders LICENSE and UCUS98716.

Put the LICENSE folder on your memory stick in PSP so it's directory is PSP/LICENSE

Put UCUS98716 in PSP/GAME so it's directory is PSP/GAME/UCUS98716

That's it enjoy your new guns...

For CFW Users:

You have to go back to ofw to use them.

Once on your memory stick just go online and edit your loadout to one of the unlocked guns and save loadout then go back to cfw.

Just keep in mind you cant change your loadout and save it after cause you will lose the guns.