GDI Text Allignment in XP versus Win7/Vista

I have a weird GDI issue:

stringFormat.SetAlignment(StringAlignmentCenter); // choose the string alignment: Left, Right, or Centergraphics.DrawString(L"BEFORE START",-1,Arial18,MPRect,&stringFormat,whiteBrush);

In Vista/Win 7 (FSX or FS9) the text Before Start will be centered as it should.However, in XP, the text is not centered. It aligns full left, even though it's the exact same gauge.Anyone seen this behavior before with GDI in XP?