Hardly the Sin of the Century, is it?
The first one, busiest, is spelt correctly. How do you think it should be spelt? As for the second, it's only the prepositional word to that has been inadvertently omitted. How many of us, myself included, have made posts on this and other Forums and missed small words like this out? The vast majority, I would guess.
Further to that, there is around 50 million or so lines of code that makes up Windows 7. It is inevitable that bugs creep in, given the sheer complexity of it. However, bugs have to be addressed according to their severity and their impact on the end user. Quite rightly, priority is given to those bugs which have been discovered to be security risks, and patches are released for these. It is extremely unlikely that a patch will be released just to correct a grammatical error, unless there is a more serious bug in the same block of code. Even then, priority will be given to the more serious bug.