Some people learned (or stand to learn) this the hard way.

"Installing Service Pack 3 for Office 2003 disables support for some Microsoft Office Excel 2003, Microsoft Office PowerPoint 2003, Microsoft Office Word 2003, and Corel Draw (.cdr) file formats are blocked."

According to Microsoft Microsoft, "By default, these file formats are blocked because they are less secure. They may pose a risk to you."

That's somewhat fair and obviously keeping in line with Microsoft's dominant MO regarding SP3, which beefed up security measures taken to protect users from malware.

Microsoft's popular Office applications (Word, Excel, PowerPoint) have forever been prime real estate for hackers, who love worming their way into all those irresistible security holes found in older file formats.

Understanding that blocking older file formats isn't the best long-term solution for a lot of users, Microsoft does allow users to override some of the restrictions implemented via SP3, and has provided a rather lengthy list of instructions to perform a manual override.

(If and when you choose to override the restrictions, understand you are also in effect reversing the point of the security upgrades and patches bundled into SP3.)

The big drawback of SP3, as far as blocked formats goes, is it simply does the blocking by default.

So, you may have already blocked earlier file formats kicking around your company archive, but you won't realize it's blocked until someone tries to access it, and who knows how long that can take.

The motivated user or IT manager is going to want to really hash out a plan to take inventory of the number of older files that may be of importance and that will need to be unblocked, rather than implementing a sweeping reversal, and therefore undoing all of SP3's security fixes.

I'm sure in the long run the potential headaches that SP3 threatens to unleash will be worked out almost painlessly, and perhaps it really will solve the unnerving security holes the Office applications have harbored.

Still, it kind of does blow that Microsoft gets to do what feels like a big fat "I told you so," to users and companies that choose not to upgrade when Microsoft tells them to upgrade.