One of the key issues in the battle between ODF and OOXML is access to documents over long timeframes. It's not just a matter of which format is better now, but which will be better in a hundred years time (assuming all the computers haven't melted by then).
Against that background, the following is interesting:
After you install Office 2003 SP3, some Microsoft Office Excel 2003, Microsoft Office PowerPoint 2003, Microsoft Office Word 2003, and Corel Draw (.cdr) file formats are blocked. By default, these file formats are blocked because they are less secure. They may pose a risk to you.
Leaving aside the fact that Microsoft is trying to protect you from its own earlier formats, there's an important issue here. Most people will blithely apply this and other Service Packs, trusting in the great god Bill to do the right thing. And then one day, they will need to access some old - but crucially important - file saved in the earlier format. All the previous versions of Microsoft Office may well have been discarded: then what?
Well, you could always edit the registry, bearing in mind:
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
Important These steps may increase your security risk. These steps may also make the computer or the network more vulnerable to attack by malicious users or by malicious software such as viruses. We recommend the process that this article describes to enable programs to operate as they are designed to or to implement specific program capabilities. Before you make these changes, we recommend that you evaluate the risks that are associated with implementing this process in your particular environment. If you decide to implement this process, take any appropriate additional steps to help protect the system. We recommend that you use this process only if you really require this process.
Er, maybe not.
There's no reason to suppose that things will be any different for OOXML, which may - who knows? - turn out to be just as dangerous as those risky old Office formats. And so there you will be, with an XML file legible only in part, with an admixture of effectively random 1s and 0s, a vague memory of its original form and contents, and a deep sadness in your heart.