For a while now, Simbin has been re-releasing most of their old favorites to Steam as GTR2 is the only of their titles not available to buy on the platform.
While new buyers can enjoy the comfort of having the title in Steam from the start, Simbin now offers the same to all owners of the boxed versions of GTR, GTR2 & GT Legends.
All owners of existing Simbin titles have to do is obtain the multiplayer lobby code that came with their title. In Steam head over to Games > Activate a product on Steam and follow the prompt until you`re asked to enter a code.
Now, simply enter the multiplayer lobby code without the dashes and the title will be added to Steam, meaning you can now play without having to worry about the old discs.
However, there seem to be limitations regarding GTR2 as not all content of the retail version is being transferred over. This is probably the same issue that prevents Simbin from selling GTR2 on Steam so far.