This homebrew allows you to swap X/O button assignment.
On Japanese Vitas O is confirm and X is cancel, while the rest of the world is X confirm, O cancel.
To change the confirm button behavior, install the vpk, then open the button-swapper bubble and follow the directions.
(Please note that using this homebrew is different from swapping X/O in Accessibility settings => Button Assignment. This homebrew "properly" swaps the buttons, without using Accessibility settings. For more information, check the source code.)