Oouh, MS Office 2003 service pack 3 is out.
You can get it here:
—- Update —-
2007-09-18 @ 20:04:
If you are working with really old file formats (i.e. pre-office 97 era), you might also want to check out this article about the file formats that will be blocked by default:
Naturally, there are of course workarounds for those restrictions – they are also detailed in the article.