When you install the Oculus app on your PC computer, it'll install on the C: drive. If you want to install the app on a different system drive, make sure the new system drive has sufficient free disk space and is formatted to use the NTFS file system.
To install the Oculus app on a different system drive:
Windows key> + R to open the Run command
[drive]:\Users\USERNAME\Downloads\OculusSetup.exe /drive=[new system drive]
[drive]with the letter of the drive where Oculus was downloaded to
[new system drive]with the letter of the new drive you'd like to install Oculus to
C:\Users\USERNAME\Downloads\OculusSetup.exe /drive=D or C:\Users\USERNAME\Downloads\OculusSetup.exe /drive:D
The Oculus app will then open and attempt to install the app on the new drive you've chosen.