Trying to sort a messy GameData folder

So, I've lost almost everything GTR2 related some time ago and got really bummed out by the thought of having to download everything again (mainly because I know most of the stuff I won't even find anymore).
I finally found a big GameData folder (120 GB or so) stored in an old HD, but boy oh boy it's a mess, it's years worth of downloading stuff and just dumping it in, and I want to do things differently this time, only keeping mods that I really like and maybe doing separate installs so booting the game doesn't take so long, since I was waiting more than 10 minutes to for it to load before.
But first things first, now I need to sort the folder so I can get only the cars that I want for the new install, the problem is there are so many files tossed around the Teams folder root (loose GMT files, DDS, GTR, TYR, etc), then we have the Sound folder, I'm pretty sure I'm not gonna need the 20 GB worth of sound files.
Is there a way to know which cars use which files? If I copy the BTCC_2011 folder inside the Teams for example, can I see if they use a specific GMT that is not inside the folder itself? Or which sound files I need to copy?
Can I do that beforehand or am I going to have to open GTR2 every time and just go by trial and error?

Also, it's been a while since I installed a fresh copy of GTR2, I remember I need the 4GB patch, is there anything else?

Sorry for the wall of text, any help is appreciated, thanks in advance.

Hello there!

Probably other people could help you in a more streamlined way, but in the meantime I can tell you a couple of hints so as to know what files each car uses. Usually, the .cas file of a car will tell you which .gmt files is using (these are usually stored in .gtr files but sometimes they are individually placed in the car's or team's folder (perhaps to override another one stored in a .gtr file). The .cas file also tells you which .gtr files are being used by that car in particular, so as I mentioned before, most of the .gmt files should be in there (or individually placed inside the car's or team's folder). With a program called GEditor you can view, import or export .gtr files too (and see what the .gmt files inside are named).

In the .hdc file you'll find which damage file (.dmg), tire file (.tyr), engine file (.eng), suspension file (.sp) and gearbox file (.grb) the car is using. Look for the lines called DamageFile, TireBrand, PhysicalModelFile, Normal, RestrictorPlate and GearFile inside the .hdc file to know which ones are in use.

The .car file tells you which .hdc and .cas files are in use by that specific car, so this is related to the previous two. It also tells you which .aud (car audio) file is in use, but in this case a missing .aud file won't cause a CTD, whereas any other of the mentioned files most likely will if any of them are missing.

The .aud file tells you which .wav (or whatever) files are in used. These .wav or whatever files are usually stored inside the Sounds folder. As missing audios don't cause CTD, this shouldn't be a top priority for you right now.

Except for .gtr files and .gmt files (and .wav files), all of the file types mentioned above can be opened with notepad.

I'm probably missing a lot of stuff, but I think you get the gist.

Well, some years ago I was in the same situation. My GTR2 was over 200 Gigs, loading time was around 7min.
I decided to clean GTR2 and deleted this and that, updating this and that. After three weeks I was very frustrated because all gets even more worse and errors was always possible. Now I decided to begin new.
1) moved my old GTR2 to a save place (do this over night, takes some time)
2) made a clean install of GTR2. From the 10th Anaversery patch you get all needed new files.
3) copy this new install to a save place
4) made some more new GTR2 installs. For instance GTR2_GT, GTR2_F1, GTR2_LM ....
simply made the folders and copy the files from your saved install into it.
This way you can always quick made a new install (I have eight)
5) now download all the mods you want and install them into the corresponding GTR2 install
Many files are updated over the years and you didn't need much files from your old install
and this way you have no or less errors and your loading times will be seconds. At the end
I only copy three mods from my old install into the new ones.

You can also use hardlinks for the Location and sound folders so you didn't need to install your tracks into each new GTR2 install.

For this whole action I need only one week and all runs perfect. There are many sites where you can
get the mods (EEC, Trackaholics, RD, ESR, F1 Classics...)

Irontower, How do you do a hardlink of the sound and track folders?  I've tried it in the config.ini file (like rFactor) but that doesn't work.  Does it require using Affinity?  I tried that once but stepped on my #$%^& by changing something and thus changing everything.  My memory span is too short to use Affinity.

I use a small freeware program "Link Shell Extension" that installs into the right click menu.
A Hardlink is done in 5 seconds with it.

Thanks.  I downloaded it.  Am working on how to  implement it.