Great, :) declaration. [DllImport("uxtheme", ExactSpelling=true, CharSet=CharSet.Unicode)] public extern static Int32 GetCurrentThemeName(StringBuilder stringThemeName, int lengthThemeName, StringBuilder stringColorName, int lengthColorName, StringBuilder stringSizeName, int lengthSizeName); and the way to use StringBuilder stringThemeName = new StringBuilder(260); int lengthThemeName = 260; StringBuilder stringColorName = new StringBuilder(260); int lengthColorName = 260; StringBuilder stringSizeName = new StringBuilder(260); int lengthSizeName = 260; if(GetCurrentThemeName(stringThemeName, lengthThemeName, stringColorName, lengthColorName, stringSizeName, lengthSizeName) == 0) { Greetz Kurt