To debug files from another solution do following

1. Inform Visual studio the path of .pdb files

select Debug-> Options and Settings
in the tree on the left, select Debugging->Symbols
on the right, in the list of Symbol file (.pdb) locations
add folders

2. Inform visual studio path of source files

In visual studio right click main solution in solution exprlorer, 
then select Properties
then, in the dialog, on the tree on the left, select Common Properties -> debug source files
add your another solution source directories on the right

3. Open required file from another solution in the main solution and add breakpoint wherever required.
4. Run main solution and you will find breakpoint are active.

To change layout of windows in visual studio  or to reset it use "Import & Export settings" from tools menu and select reset and follow the wizard to change layout to General, Test, Web developer etc.