If you want to change number of rows on Windows 8 metro, refer to the tutorial below.
Microsoft is full of surprises. In the developer’s preview version of Windows 8, Microsoft introduces Metro user interface. In metro user interface, you can see everything in tiles in several rows. The numbers of row depend on your desktop’s resolution. If your desktop’s resolution is 800 X 600, then there will be 3 rows. If you have 1366 X 768, then you will have 4 rows. There is another way of changing the number of rows except from changing resolution. To change the number of rows, read the instructions carefully.
1. Open the Run Dialog Box by pressing Windows + R. Now type regedit and press Enter.
2. Navigate to the registry key HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\ImmersiveShell\Grid.
3. Now right click on empty pane and click on New. Now click on DWORD(32-bit) value. Name the new key as Layout_MaximumRowCount.
4. Now right click on this key and select modify. Change the value data to 3 or 4 , depending on your need.
Now you can see that value is set to 3 beside this key.
5. Now click the OK button and close the registry editor.
Log off from your current user account.
When you log in again you will see 3 row in the metro user interface.
In future if you want to change the row number then change only the value in the registry.