Missing MS SystemEx font

After installing Lynotype FontExplorerX (a font managing program to
(de)activate fonts on the fly) I have a problem with a missing font: MS
SystemEx. To be brief: FontExplorerX also manages system fonts by placing
them in a special folder and adding a shortcut to the font in \windows\fonts.
This process is not flawless: some fonts are deleted instead of moved to this
special folder. I notified Linotype of this; the reply was: they know the
problem, it will be corrected in the next version of the program, re-install
the missing fonts (from original Windows CD).
After I re-installed the fonts, I still get the warning that Outlook 2007 is
missing the font MS SystemEx, Bold. I cannot get any information about this
font, not at the Microsoft sites, or when searching Internet.
Does anybody know what this font is and inform me of how to install it again?

Thanks for your cooperation.