There's been a lot of misinformation about Windows 7 going around. So here's why I think all these rumors are just plain incorrect:
Rumor: The next version of Windows is codenamed "7", Windows Seven, Windows "7", or Windows Se7en.
Reality: The next version of Windows is codenamed Windows 7.
Rumor: Microsoft plans to ship Windows 7 three years from now.
Reality: Microsoft plans to finish Windows 7 three years after they started working on it.
Rumor: Bill Gates said Windows 7 would ship next year.
Reality: Bill Gates said "sometime in the next year or so" they "will have a new version."
Rumor: Windows 7 is being rewritten from scratch or near scratch,.
Reality: Microsoft has made it clear that Windows 7 is an evolution of Windows Vista. Also, they never said they were throwing away any code. They're merely making it possible for them to build a small part of the OS ("MinWin") without the rest of Windows, probably just for testing the kernel.
Rumor: Any screenshots claiming to show Windows 7's GUI are fake, as Windows 7 is just MinWin right now.
Reality: As I said before, Microsoft never said they were throwing away any code, or that they weren't working on the GUI yet.
That's all the major misinformation I can think of right now. I'm gonna add links to my sources if/when I get around to it.