1. This is how the Metro Menu on my screen looks like before any changes
2. Execute Run and type in regedit and press Enter
3. Go to the following Key:
You should see the Layout_MaximumRowCount key on the right hand side. In case you do not see it, you should be able to create it. Right click anywhere in empty space, click New and Dword (32-bit) value. Once the key has been generated, rename it as Layout_MaximumRowCount
Type in the number of rows that you want and press Enter
Once you are done, just sign out and in to witness the changes.