I said that it was interfering with my mp3 player also plastic (with metal parts) - where was I, oh yes the usb stick, the metal end was a bit loose so I pushed it into the slot more firmly, and it works. Then the landline phone went so I spoke to the shop owner. The pens therefore work on this pc (which might be hackable by a local hacker, either one of the shops or one of the flats above them linked by email to the fire, ambulance, and police - cctv out on the main road -) but is not scannable or usable on the shops' main computer. Hmm, I wonder why that is?