There have been plenty of programs I've used that either didn't work or were so poorly designed that I couldn't figure out how to use them, so I just gave up and used something else. I don't remember them off-hand though. So one thing that does come to mind is Windows 95. It would crash constantly. And it didn't help that, with the hardware limitations of that time, it ran really slowly. Nowadays it would run faster (probably blazingly fast), but I think it would still crash. If it would even run on a modern computer--I'm not sure. Though, even if it would, aside from the crashing, it wouldn't run any software you can easily get nowadays, and probably no web browser you can run on it would be compatible with any modern website.