PSP Memory  

I don't understand your question very well... but if i understand the only thing that you can do to add external memory is buy more Memory Stick PRO DUO. To install new version games you only need to copy this updates to memory card.

Good Night

i am afraid you could not add external memory to PSP. do you mean you want to add memory stick for PSP. it's different concept between memory and memory stick. the memory like the memory of PC, while the memory stick as hard disk of PC.