The background loads but explorer.exe doesn't load. We can get onto this via ctrl+alt+del and opening task manager then running the new task "explorer.exe"
Go to your registry (open start menu, choose 'run' and type in regedit.exe). There, go to the following key: [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon] There you should see a 'string value' called "Shell". If you double click it, the value should be "Explorer.exe". If there is another value, or some parameters following this, change it. After that, restart your machine.
For more information, also see this post. Third option is what I suggested.