PLEASE NOTE: MY RIFT HASN'T ARRIVED YET, THIS COULD BE THE CAUSE.
I downloaded the latest version of Vireio Perception, just to see what it could be like, even though I had pretty low expectations, and ran it as administrator, as is suggested. I then opened Steam as administrator (also suggested) and launched Left 4 Dead 2. Left 4 Dead 2 looked exactly the same on my monitor, even in game, so I exited. Since then, I have tried every setting I could find in Vireio Perception, tried not running them as administrator, etc.
Since Left 4 Dead 2 is the only supported game that I own on PC, I can't really try it on another game. Also, I'm not sure if I downloaded the wrong version of Vireio Perception.
As stated before, my Rift hasn't arrived. I don't know if plugging in the Rift plays a part in the way that Vireio runs.
Thanks in advance.
Oh, the brutal wait until Christmas. Downloading leagues of demos to make the wait less agonising.