Disclaimer: I'm not a user interface designer or anything person to this is just my opinion as a user... I agree, its best to minimize error messages, however.

Disclaimer: I'm not a user interface designer or anything person to this is just my opinion as a user... I agree, its best to minimize error messages, however... why didn't it just do that, maybe a few times, before even thinking of bothering the user? How do you know it didn't (aside from assuming MS is dumb/lazy/etc...)? In any event, this is a case that can come up, and, as the post says, the error message is bad in almost every way. perhaps the web page could figure out the closest valid key and just log in using that key (or have a Google-style "did you mean XYZ-123-ABC" link for the matching key). This is actually a tougher case than just that. In fact, the problem seems to start before the error message. If there are two ways to register 1) Sign up for a username/password 2) Enter a key You should be entering these in different fields and/or pushing different buttons and/or having these on different pages. This shouldn't even happen to begin with! What did the screen look like? Was the user supposed to type the key into the password field? Thats silly, incorrect and confusing. About your suggestion for finding a nearby key... I suspect that would be problematic. People use 16 character keys to make them hard to guess. Since only a small number of the 16 character combinations are valid, a random guess is unlikely to succeed. The more leeway you give, the less effective this is. For example... if you allow any two adjacent characters to be swapped, you increase the number of "valid" keys by a factor of 15 (of the 16 characters, each of the first 15 can be "swapped" with the next one).