Has someone sent you a .docx file yet? That's the Word 2007 file format.  (The new Excel format is .xlsx, the new Powerpoint is .pptx, and so on.) The first time I tried to open one with Word 2003, I got a helpful dialog offering to get and install the converter for me, and I did, and now I can move the files back and forth around my network without concern. But a few people have mentioned to me that they didn't get this helpful dialog. You can hand-download and install the converter from the Office preview site. Make sure you are up to date on Office Service Packs... there are links from the download page. And though the converter says it's for the Technical Refresh 2, it has worked fine for me on files created with earlier betas.

Kate