If I download a game via Steam and then format my PC, how can I recover my game?

[76561198262902940]

This question is for my friend. He has to format his PC because of some problems but he has installed many games via Steam. For some reasons, he has to format the whole computer so even if Steam isn't in C drive, he will lose everything. Can we keep his steamapps data in an external storage, install Steam when he's done formatting, and paste that directory back to Steam's root directory? Or will he need to reinstall all those games again?

[Typo Hui]

Yes you can save the steamapps folder and move it into the new steam installation folder. Do keep in mind that you will also need to save/backup your game saves too which varries for each game. I put the full list below, but if you want the common locations: Your window's user folder, your documents folder, your AppData folder and finally in the game folder itself which you are saving.

It's been a little while since I did this, but I think there might be a first time installation when you run the game for the first time on the new build. Nothing big, but it's worth saying this could happen.

General Windows locations
[DOCUMENTS] -- The default location for the "My Documents" shell folder/library
Windows XP: C:\Documents and Settings\[USERNAME]\My Documents\
Windows Vista: C:\Users\[USERNAME]\Documents\

[APPDATA] -- The default location for standard application settings
Windows XP: C:\Documents and Settings\[USERNAME]\Application Data\
Windows Vista: C:\Users\[USERNAME]\AppData\Roaming\

[LOCAL] -- The default location for system-specific application settings
Windows XP: C:\Documents and Settings\[USERNAME]\Local Settings\
Windows Vista: C:\Users\[USERNAME]\AppData\Local\

[PUBLICDATA] -- The default location for cross-user application settings
Windows XP: C:\Documents and settings\All Users\Application Data\
Windows Vista: C:\ProgramData\

[PUBLIC] -- The default location for cross-user system settings
Windows XP: C:\Documents and Settings\All Users\
Windows Vista: C:\Users\Public\

[SAVEDGAMES] -- The Windows Vista default Saved Games folder
Windows Vista: C:\Users\[DOCUMENTS]\Saved Games\
Windows XP: I do not know of any Windows XP analog for this location. If someone does, please tell me.

Credit to Kailieann for this list:
http://forums.steampowered.com/forums/showthread.php?t=840657

[ReBoot]

Use Steams backup function. And before you worry about savegames, check I the game uses Steamcloud.