I have an older computer, one whose keyboard is ATTACHED, and some of the keys aren't working. I tried taking them off and cleaning them, but still -- no result. To be specific, the number keys from 4 to 9 aren't working (that is, 4-5-6-7-8-9). These are the only unusable keys on my keyboard, and I kind of NEED to use them. The keyboard viewer does however work, but it takes too much time -- when writing an urgent email, for example.