Holy cow, I wrote a book!
Two customers (so far)
wanted to know how to increase the duration of
taskbar balloon notifications on Windows Vista.
(By the way, I gave the answer
some time ago.)
They claimed that on Windows XP, they were using
the registry key
setting the value BalloonTip to a
REG_DWORD specifying the number of
seconds the balloon should appear.
They wanted to know if this still worked in Vista.
Heck, it didn't work even in Windows XP!
That undocumented registry key actually controls whether
the Windows XP taskbar
should show the "To see the hidden icons,
click this button" tip.
It has nothing to do with how long the balloon stays
on the screen.
A quick Web search suggests that that particular
setting has reached cult status,
with everybody saying that the setting controls
and nobody actually testing it.
It's just a matter of faith.
Even the sometimes-suggested trick of
putting the registry key name in MSDN so searches can find it and
direct users to the correct method
wouldn't have helped,
because this was the wrong registry key to begin with.
(Remember, the answer
the linked article.)