Run, as quickly as you can, and purchase XP while you can -- not that you will be better off...that is...really.
Oh, and yes its true, Microsoft Office 2007 is not backwards compatible with earlier versions of itself, unless you can easily train your staff to "Save As"... Oh yeah, I've tried this type of training, it's as elusive as dark matter.
Beware the .docx - you have been warned!
More... How Microsoft is destroying personal productivity...
The TRAIL OF TEARS:
Microsoft to simplify downgrades from Vista to XP
Even Softies get the Vista installation blues
From the 'I'm glad I'm not a Vista salesperson' files