You should have C:\Program Files\VDrift\data\skins\simple\textures as well as C:\Program Files\VDrift\data\textures - the former is the graphics for the skin, the latter is graphics that are used in different parts of the game.
Can you try finding your VDrift.config file? It should be in C:\Documents and Settings\your user\Application Data\VDrift - or something along those lines. I don't have a Windows box handy to make sure, and that hasn't been added to our documentation wiki yet. I'll try to clarify the location soon...
edit: The correct location is
C:\Document and Settings\username\.vdrift\VDrift.config. Sorry for the confusion...
Anyway please try changing the line "texture_size = medium" under the [ display ] section to "texture_size = large" and see if that fixes the graphics problem. If it does, that means it's a problem with SDL_gfx, if not, then it's something else...
Thanks for your help