Outside of On-Live, there hasn’t really been a scene for renting PC games in the traditional sense, probably because you can install them, send the disc back and then enjoy the title as if you bought it. But Direct 2 Drive is giving a similar formula a chance, now allowing players to pay $5 for five hours of gameplay.
After choosing which game you wish to rent, you download the entire game to your computer. Once your five hours are up, you have the option to purchase the title at full price, with the initial $5 investment put toward your purchase. So basically a five hour demo for a fairly reasonable price.
As of right now, D2D is offering this for only a handful of titles: Silent Hill: Homecoming, Grid, F.E.A.R. and Divinity 2. But surely if it gains popularity, it will expand.
(Source: Direct 2 Drive Blog)