I just won an auction for a 4GB Pro Duo mem stick to use with my PSP at a decent price of just over $20. I noticed that the auction said it was for a certain camera, with no mention of PSP. I just assumed that the Pro Duo format was all the same. Did I just screw up? Yes, I googled, but I couldn't find a satisfactory explanation. I'm inclined to think that it will work, but does anybody know of differences between Pro Duo sticks that would not allow it to work in the PSP?