Steam installs to the following folder by default:
Files for games installed on Steam are stored in the following folder:
During the installation of Steam, you have the option to install Steam to a location other than the default. Since Steam relies on the game files residing in the SteamApps folder, your game files will go to whatever folder you have Steam installed in. The game files must be in the SteamApps folder in order to function.
Moving Your Steam Installation
It is highly recommended that you create a backup of your SteamApps folder before attempting this process. Neglecting to do so may result in a loss of all of your game content should something go wrong.
If you're low on space on the drive you have Steam installed, you can move the Steam folder to a different location. Here's an example of how to move the Steam installation between two hard drives:
1. Log out and exit Steam
2. Navigate to the folder where Steam is installed (by default: C:\Program Files\Steam\)
3. Delete all of the files and folders except the SteamApps folder and Steam.exe
4. Cut and paste your Steam folder to the new location, for example: D:\Games\Steam\
5. Launch Steam
6. Steam will briefly update and then you will be ready to play
7. All future game content will be downloaded to the new folder D:\Games\Steam\Steamapps\