No problem. Glad it helped

To step through the framework code, simply open up the source code and build it in debug mode.

When I try to Rebuild Inherited UI I get 102 errors and 11 warnings.

Next, get out of Visual Studio, go back in. You should now be able to step into the SF source. Let me know if that doesn't get you going.

I couldn't build Inherited UI - I got 103 errors and 11 warnings. Got out of VS and went back in - still cannot step through framework code

Inherited UI is for DevExpress controls. If you are not using DevExpress then you do not need to build this assembly. Otherwise, you need to change the references of this project to match your current DevExpress version.