Heh! That "Ka-Ka" is kaka in russian too :)

5.0 is very outdated for me. It miss many properties present in 6.0 which I heavily use.

It seems that system window classes are used to theme old applictions. (Previously in this thread I described the way to theme old applications using *.manifest file. It works fine for such apps as HTML Help Workshop created w/o any idea about XP themes).
I guess that MS didn't use system window classes in 6.0 for some reason. But why?

.NET does not use any ActiveX control. All .NET classes are stored in .NET Framework class library. This is very similar to Delphi VCL except that stand-alone class libraries are not compiled into exe.
I see that WinForms classes have more features than thair analoges in Common Controls ActiveX libs.