What a lot of people might not know is that when you change your computer you do not have to re-download your Steam games. Now that the Steam sale is done and a lot of people will have amassed a huge library, this is an incredible feature to know. You can even move your game files to another drive in the same computer if you want to save up space. Do not follow the steps below before you check out the notes in the bottom.
The process is very simple. If you have the Steam client open, exit it. Go to your Steam folder, usually located in C:\Program Files\Steam. Delete all of the files in there except for the SteamApps folder and the Steam.exe file. Cut and paste the remaining files to wherever you want them to be next, be it a new computer or a new drive. Run the executable file and Steam will update itself so that you can continue normally.
Although all of that is very easy to do, there are some very important notes that you should follow through. First of all, some of the save files will not be located in the SteamApps folder. Some might be located in the userdata folder while some might be stored in your Documents. Check each game individually if you do not want to lose your data. Furthermore, something might go wrong in the process. There are two ways to solve this. First of all, before doing anything, backup your game files by right clicking on any game in your Steam library and choosing the appropriate action.
Finally, if something is wrong with a game after you have moved the files, you will need to verify the files. This is extremely simple as well. Right click on any game of your library and select Properties. Go to the Local Files tab and choose the “Verify integrity of the game cache” option. Steam will then check the game files and replace any damaged files with the correct ones. Keep in mind that some custom files might appear as broken but this is normal.