If you ever get problems launching or running C&C: Remastered, you might find out that a lot of these problems are not down to the bare installed game files, and the obvious solution, to go into the game's Steam settings, go to "Local Files" and use the "Verify integrity of game files" function, does not help you out.

In these situations, the issue is probably in some configuration file or caching mechanism. So it's handy to know exactly what files the game has stored outside its main game files.

I will not give specific instructions on what to backup / delete / keep here. I honestly don't know enough about the internal workings of the game or Steam to give such advice. But if you want to make an absolutely 100% clean reinstall, this guide should give you an indication of what folders to delete.

Notes:

• In this guide, I will very often use a notation between percentage marks (like %appdata%). These are in-built Windows shortcuts for folders. You can paste just the part with the percentages into the address bar in your files explorer and press enter, and you'll see where it ends up.
  
• Likewise, I use <Steam games library folder> to refer to your Steam games library folder. By default, this is C:\Program Files (x86)\Steam. If you changed that, though, you should obviously know where you put it.
  
• A third one is <your Steam user ID>. This is the numeric ID of your Steam account. When you open your Steam UserData folder (see below), there should be numbered folders in there for any Steam users that have logged in on your PC. It shouldn't be hard to determine from there which folder (and thus, number) is yours.
  If it is a problem, you can still find out rather easily: inside each of the numbered folders, under sub-folder "config", there is a file called "localconfig.vdf". Open that (unless you have something more advanced like Notepad++, select "WordPad" as application to open it), and in the text, look up the same numbered folder you opened it from, and, under "friends", you should see the number listed, followed by the actual name and the user's known name history.
  
• The number "1213210" will appear a lot in this guide. It is the actual Steam ID of the C&C: Remastered Collection. You can easily see that in the address bar of the Steam store and community pages for the game.

Main game install folder and installed app info file:

• <Steam games library folder>\steamapps\common\CnCRemastered\
  Note: beta testers might have a folder called "Telstar - CCR" instead.
  
• <Steam games library folder>\steamapps\appmanifest_1213210.acf

Downloaded workshop content, workshop cache, and crash reports:

• <Steam games library folder>\steamapps\workshop\content\1213210\
  
• %appdata%\CnCRemastered\

Synced game settings and savegames: (might be worth making a backup of if you reinstall)

• %ProgramFiles(x86)%\Steam\userdata\<your Steam user ID>\1213210\

Screenshots: (760 is the steam ID for the "screenshots" functionality)

• %ProgramFiles(x86)%\Steam\userdata\<your Steam user ID>\760\remote\1213210\

Unpacked workshop maps, replays, and user added mods/missions:

• %userprofile%\Documents\CnCRemastered\

Map editor settings: (if you have issues, delete this and let the editor re-generate it)

• %localappdata%\Electronic_Arts_Inc\ → folder starting with "CnCTDRAMapEditor.exe_Url_"
  
• For the upgraded map editor[github.com], this is under "%localappdata%\Nyerguds\"

Not sure if this is worth touching. Most of it is probably just downloaded from the Steam servers.

Achievements cache:

• %ProgramFiles(x86)%\Steam\userdata\(your Steam user ID)\config\librarycache\1213210.json

Workshop subscriptions list:

• %ProgramFiles(x86)%\Steam\userdata\(your Steam user ID)\ugc\1213210_subscriptions.vdf

Shader cache:

• <Steam games library folder>\steamapps\shadercache\1213210

Just for the sake of completeness:

• %ProgramData%\Origin\LocalContent\CnCRemastered\