I'm not sure what a PSP is referring to, but you might want to check power supply.
I had a similar problem a year or so back w/ and ext. HD. I plugged it into a USB and it would not work or be recognized. It was because THAT USB was not on the mobo (i.e. not enough power). So I switched the cables, and plugged it into a USB that was ON the mobo, and tada. Worked.
Some USB's do nto provide enough power for external add-on's, so you have to use the power cord, or make sure that you are plugging into a USB on the mobo where it gets enough power.
I've never owned a laptop, so I am not sure of the power available on mobo's for the add-on's. But try switching the USB cabling around, or use a power source for your PSP.
