It isn't clear how it got to be commented in your version of the file. But it is clear that you don't hesitate to edit compiler header files to get out of a problem. You may have done this before to bypass a problem and not remember it.
In general, this is a Really Really Bad Idea. Microsoft releases service packs and security updates that will update compiler header files. But it will not do so if the file was altered. Which may leave you with a nasty mixed bag of files that are no longer compatible with each other.
You will need to fix the damage done to these files. Pay attention to the modified timestamp of these files to find out which might have been changed. And copy those from a known-good machine of, say, a friend or colleague. Another possible approach (never tried it myself) is to move the altered files somewhere else and run setup again, asking for a repair. Not actually sure if that works, it should. Also re-apply service packs when you do it that way.