Holy cow, I wrote a book!
There were various capability GUIDs defined, things like
GUID_CanStretchAlpha to ask the driver whether it was
capable of stretching a bitmap with an alpha channel.
There was one driver that returned TRUE when you called
DoesDriverSupport(GUID_XYZ), but when DirectDraw
tried to use that capability, it failed, and in a pretty
So one of the DirectDraw developers called the vendor and
asked them, "So does your card do XYZ?"
Their response: "What's XYZ?"
Turns out that their driver's implementation of DoesDriverSupport
was something like this:
BOOL DoesDriverSupport(REFGUID guidCapability)
In other words, whenever DirectX asked, "Can you do this?"
they answered, "Sure, we do that," without even checking what
the question was.
(The driver must have been written by the sales department.)
So the DirectDraw folks changed the way they queried for
driver capabilities. One of the developers went into his
boss's office, took a network card, extracted the
MAC address, and then smashed the card with a hammer.
You see, this last step was important: The GUID generation
algorithm is based on a combination of time and space.
When you ask CoCreateGuid to create a new GUID, it encodes
the time of your request in the first part of the GUID
and information that uniquely identifies your machine
(the network card's MAC address, which is required
to be unique by the standards that apply to network card).
By smashing the network card with a hammer, he prevented
that network card from ever being used to generate a GUID.