i put my memory card from my sony ericsson k750i into my psp?

Probably nothing.

if both devices use the same type of card, itll work

what type is it? CF? SD?

but whatevers on the card might not work depending what files they are

sd card with photos and music on

they are both the same card but 1 as just got more memory on it

if the psp reads sd cards (ive never used a psp so dont know) then yeah it will work, same if the psp runs those picture / music formats itll play the music etc

same as my ds uses sd cards.........same as my camera and my card reader on the pc

cheers chaps