Holy cow, I wrote a book!
Among the things you can get with
the GetStockObject function
are two fonts called SYSTEM_FONT and DEFAULT_GUI_FONT.
What are they?
They are fonts nobody uses any more.
Back in the old days of Windows 2.0,
the font used for dialog boxes
was a bitmap font called System.
This is the font that SYSTEM_FONT retrieves,
and it is still the default dialog box font
for compatibility reasons.
Of course, nobody nowadays would ever use such an ugly font
for their dialog boxes.
(Among other things, it's a bitmap font and therefore does not look
good at high resolutions, nor can it be anti-aliased.)
DEFAULT_GUI_FONT has an even less illustrious history.
It was created during Windows 95 development
in the hopes of becoming the new default GUI font,
but by July 1994, Windows itself stopped using it
in favor of the various fonts returned by
the SystemParametersInfo function.
Its existence is now vestigial.
One major gotcha with SYSTEM_FONT
and DEFAULT_GUI_FONT is that on a typical US-English
machine, they map to bitmap fonts that do not support ClearType.