MsiProcessMessage shows improper icon

Hi,

I've used MsiProcessMessage to show error & information messages to
the user. My installer always runs in the basic (/qb) mode.
The installer displays messages and associated icons properly on Win
XP, Win 7 & Win 2003. But, on Windows Vista & Windows Server 2008, it
shows different error & information icon.

However, if I show the error messages using MessageBox() API, it shows
proper icon.
Did I do something wrong? If not, can anyone justify this behavior?
Moreover, can I specify custom icons for displaying them in messages?

It's kind of bizarre that though the icons get shown properly in
Windows 7, it's predecessor (Vista) doesn't show 'em properly. If that
were a bug, then why Win 2008 server, which is released after Win 7,
is shipped with this bug?

Thank You.
PS.