As for the "button grid," that's the control focus, and it happens on just about every button in Windows.
Regarding titlebars, it wouldn't be a good idea to do that; there's no guarantee that the titlebar text isn't already centered (like if some theme did that already) and if that was the case, it would just look screwy.
As for MCI errors, if you have VC++, you can use the mciGetErrorString() function.
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