Hi this depends on the way you are connecting it.
I suggest that you try the following:
1) Unplug the Parallel adapter from the ADC212 and from the computer.
2) Close any Pico Software.
3) Plug the adapter into the USB port WITHOUT the ADC212.
4) Go into device manager (Right click on my computer and select properties then select Hardware and then choose Device Manager) Check under "Universal Serial Bus Controllers" if the "Pico Parallel Port" appears.
If not then check if there is a device that says other devices with a yellow exclamation mark.
5) If the device appears, then plug the adapter into your ADC212 and load the software. Make sure that when using PicoScope 5 you select "File->Setup->Converter" and that if you are using the USB that USBPP1 is selected and if you are using the parallel port that the appropriate LPT is selected.
If you are using PicoLog also make sure that the appropriate connection is chosen.
Let me know how you get on.