Instructions
Make sure the PSP is plugged in, powered on, and in USB mode. All three of these conditions must be met if the computer is to recognize the PSP. If you have forgotten even one of these components, the computer will not recognize the device.
Make sure the Memory Stick Duo is formatted inside your PSP. If the memory stick is not formatted correctly, the computer might have problems identifying your PSP. Format it by going to the "System Settings" tab, highlighting "Format Memory Stick" and then pressing the "X" button.
Try a different USB Cable/Port. The PSP uses a standard mini-USB cable, so if the one that came with your PSP isn't working, try using a different one. You can also try plugging it into a different USB port. If you were using a standard USB port, try plugging the PSP into a hi-speed 2.0 USB port.
Restart your computer. If all else fails, try restarting the computer and then try to reconnect. Sometimes computer performance can interfere with the function of its ports. If your computer is experiencing freezing or extreme slowdowns, try restarting the computer and then try to detect the PSP again.