Can some one put me straight

I've been reading all the news for windows messenger 5 and I am getting
confused with all the different views. I understand windows messenger is for
corporate businesses and MSN messenger is for home use. I use Windows
messenger because of the options it offers like application sharing, etc Can
someone help me out by putting me straight.

1. Is windows messenger 5 for XP or not
2.Will it be an upgrade for Windows messenger 4.7
3.If it is not an upgrade is it to replace windows messenger 4.7
4. Will windows messenger 5 still work together with Outlook Express
5. When is it due to be released
6. Where can I download it once it has been released.
7. What is the real difference that is being made to windows messenger 4.7
to windows messenger 5.0

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William