I was trying to help a friend recently with a bizarre issue with a Dell laptop: the 2 key (and only the 2 key) is unreliable. Normally I'd say "hardware problem" but it acted more like a software bug. Among other signs, it's unreliable in Windows and the BIOS but not in Linux.

Unfortunately, I don't have the skills to even diagnose the problem, let alone fix it. And my friend isn't willing to put Linux on it since he wants to sell it.