Computer lock VS Calculating castle

A week ago I tried to go to different shops to buy a computer lock ... I thought. As I tried to pronounce it: POČITAČ ZÁMEK I think most of them the first time heard: POČITAT ZÁMEK before they made a strange face to me,bended my pronounciation to the correct form in their brain and finally gave me an approving smile as a gift of that they finally understood.

Computer .... lock
VS
Calculating castle

Note: Although I finally ended up buying a computer-lock for 1000 CZK (250 NOK) - it would be a real bargain to have a real and fully functional calculating castle for the same price.