Do you mean that when you open a .jpg file, PSE is the software used to open it?
as soon as I enter a memory stick into the USB-slot, and there is a jgp file on the stick, PSE starts (and blocks the computer for 40 seconds).
are you using windows? if you are, try disabling it under msconfig
Another resolution: Change the Autoplay settings
Follow these steps to specify what should happen when you insert different types of digital media into your computer.
Under Media, find the type of media that you want to change the AutoPlay setting for.
Click the action that you want AutoPlay to take when you insert that type of media into your computer.