@Ekey: Nice find.

@Chipicao:
You can see some XML in startup.dat, some parts of English sentences in localization.dat and DDS textures compressed with DXT5 like in greatcanyon.dat.
If the geometry data of the cars is compressed, it's not part of the fat/dat format.

Strange: The .dat files weren't compressed or encrypted. You can see plaintext. But it looks like the files are mixed together.
Unfortunately, I can't compare it to FC3 because I don't have it. Is there some documentation about the FC3 format?

After starting MultiEx Commander in compatibility mode, you can change the settings back to normal again.

I extracted the sound from StreamsMulti.pck with AlphaTwentyThree's WAVE format scanner, ww2ogg (using included packed_codebooks_aoTuV_603.bin) and revorb.

This script doesn't work for PC version. QuickBMS generic files extractor and reimporter 0.5.17b by Luigi Auriemma e-mail: aluigi@autistici.org web: aluigi.org - open input file D:\Steam\SteamApps\common\Sonic & All-Stars Racing Transformed \Data\sound\StreamsMulti.pck - open script darksiders2_...