When I first set up a computer for my parents, about 5 years ago, I remember all the trouble I had teaching my father how to double-click. "You have to press twice," I told him, "quickly." When this didn't work, I didn't know what to do other than repeat the instruction. I think I eventually also found some setting to twiddle with in Windows that helped with the matter, but he still struggles with it sometimes. I mean, he's got that first click down pat, but something about the second click he just can't fully cotton onto.
I got my Tablet PC today. I haven't had much time to play with it. But, the big problem so far: I can't quite seem to get the hang of how you double-click.