MyComputer as initial directory

Answer 1

My Computer is a virtual folder. It has a predefined GUID. Here is how you get My Computer

 OpenFileDialog d = new OpenFileDialog();
 d.InitialDirectory = "::{20D04FE0-3AEA-1069-A2D8-08002B30309D}";
 d.ShowDialog();

If you want to know about special folders

http://msdn.microsoft.com/en-us/library/system.environment.specialfolder.aspx

but be aware of

The MyComputer constant always yields the empty string ("") because no path is defined for the My Computer folder.

Answer 2

A good way to handle this is using the "special folders" in the .NET Environment library.

For instance, the "My Documents" (personal) would use:

Environment.GetFolderPath(Environment.SpecialFolder.Personal)