problem with installing new webcam?

I have bought a webcam in argos, product brand is trust. i tried to install it but the computer says "unable to find software". I thought it might be a factory defect of the webcam itself so i ask argos to change it. i ended up changing it to mikomi 1.3mp bec my previous webcam was a mikomi mobile and "that works". It still say software not recognized despite of me installing the software as intructed. i called packard bell to ask for advice and they say the problem might be the webcam but we have changed the webcam 3x. I test the USB port with my cellphone and definitely it is working. can you advice me on what else to do. i have window xp.