That would include me. I still use Office 2003.
This is a classic Microsoft PR gaffe. Routinely, the largest software company in the world forgets it's obnoxious to act like the largest software company in the world feeling entitled to act without sensitivity to its customers.
Microsoft's new Office 2007 is built on its new pride and joy format, Office Open XML (OOXML), designed to be more secure from hackers.
In its enthusiasm to convert us all to OOXML, Microsoft took the draconian step of making it impossible for Office 2003 users to access older file formats. This has gone over like a lead balloon in recent days.
Microsoft gets it and has done an about face. Microsoft blogger, David LeBlanc has a deeper explanation of what happened and, more importantly, a list of links to download the appropriate patches to fix your formats.
Microsoft desperately wants the International Standards Organization to adopt OOXML as an industry standard. Earlier votes taken back in September didn't stack up in Microsoft's favor. Next month, the ISO will review submitted modifications to see if enough members want to change their votes in Microsoft's favor. Clearly, bad press like this wouldn't help.