This is a problem caused by a codec pack, part of Morgan Stream Switcher. I had this problem when I first tried to run WinSPMBT on an XP machine.
I fixed the problem by installing and uninstalling mmswitch.exe using the following download link:
http://www.morgan-multimedia.com/download/mmswitch.exe
This ensures it is correctly uninstalled. The manual method is to find and delete MMSwitch.dll and MMSwitch.ax but this method may leave spurious Registry entries.
If other applications use this codec you might have a problem with something else, but I've had no adverse effects at all.
If you're still not sure Google mmswitch.ax and see what other people have to say.
Good luck,
Tim