The oculus setup has downloaded and has been 'installing' for 3-4 hours. Since there is no progress bar it's not possible to see if it's stuck or not (I'd guess it is).
Already restarted the PC and installation (as administrator). After waiting 1.5 hours.
Make sure your computer meets our recommended System Specifications. Checked using the Oculus Tool
Make sure you're signed in as a Windows user with the necessary permissions. Ran as admin
If you're on Windows 7, make sure you have .NET Framework 4.5 installed. Microsoft .NET Framework 4.5 Multi-Targeting Pack is installed
The PC has Windows 8.1