I'm kinda struggling getting these to work together.. According to Simbin, Race Injection is the final expansion completing the series. However, while I have the offline DVD version of GTR Evolution and the online Steam version of Race Injection I can't seem to find a way to combine them, they install as two seperate games in seperate directions. Is there a workaround to have all cars/tracks/cups/etc. in one game, preferably Race Injection as it is the most recent? As Race Injection is yet another set of expansions, it seems to me this should be possible.

The expansions were all designed to work with the steam version of Evo. I think Race Injection does have a DVD version but even that links into your Steam account.

IIRC The GTR Evo DVD contains both the offline and online (Steam) versions. Stick the DVD in and run the setup. Choose "Online Steam Install". It will install Steam, Race07, and the GTR Evo addon. You can then install the expansions.

If that doesn't work, the only other thing i can think of is to extract the .gcf files from your Steam folder and copy them to your install.

You shouldn't need to use the DVD, you just need the reg number that comes with it.

Start Steam and then in the top right corner click on "Games" and choose "Activate a Product on Steam", then put the key in when when it tells you.
Steam will then download the needed files. It will download the files even if you use the disc anyway.

Uh yeah.. That's kinda the problem. I can't use the online Steam version. I need to stick with offline DVD installations.

Er well in that case your left with Darren's suggestion of extracting the .gcf files
Do a search for GCFScape