Microsoft's most proprietary (and formerly danger-prone) graphics file format is the Windows Metafile. Some of these files, with the file extension .wmf, could be found in Windows itself but today you will find them mostly in supplied Microsoft Office clip art. I found over 1,600 WMFs in the Program Files folder on my laptop.
It has always been something of a challenge to edit or create these files. I own a program called Metafile Companion, the only commercial editor of which I am aware. The program has been at version 1.11 for a very long time although it does run in every version of Windows since 95.
This morning it occurred to me that Microsoft might have included support for WMF in Expression Design. Sixty seconds later I knew it was not supported - Design would not open a WMF.
To be fair, WMF is a dated format. The XML-based scalable vector graphic (SVG) is an emerging open standard likely to be supported by all Web browsers in the future. Microsoft itself has moved to XML-based graphics descriptions, evident in the Expression family.
Still, I thought it was strange that Microsoft did not provide support for its own format in its first significant foray in to graphics editing.