I downloaded Alliance of Valiant Arms some while ago.. before installing windows 7 I just copied the ava folder into a temporary partition. Now I am trying a direct copy and paste from that partition to steam/steamapps.. except that isn't working. Can I get i working without downloading AVA all over again? I want to download Planetside 2 from steam.. but if I have to download again whenever I change OS or computers it's going to be a PITA and not worth going over the bandwidth limit. Any ideas?
It looks like you may have forgotten the cache file. Steam needs those to know what files are required for each game.
I have done this on my own computer while I was upgrading my OS. There is no need for any special backup feature or middleman program or function.
Browse to your SteamApps directory, then check the common directory. Is your game in this folder? If not, check in the folder with your Steam Login name.
Move, not copy (right click and drag) that folder wherever you like for the backup. It's easier if you mimic the directory structure in the actual SteamApps folder.
Consult the AppID list for your game's ID number (Alliance of Valiant Arms is 102700), then move the appmanifest_ID.acf (ex. appmanifest_102700.acf), game name here.gcf or game name here.ncf file to where you placed your backup.
Place the folders back exactly where they were when you copied them away from Steam. The game's folder back in Steam/SteamApps/common or Steam/SteamApps/[Username], the ACF, GCF or NCF in Steam/SteamApps.
Games that you own will have to be "re-installed" again. Steam will find what you copied back into SteamApps, then download anything missing.
Any Free-to-Play game is not going to be in your library when you open Steam again. Just browse to it's store page and click install. Again, Steam will find what you copied back into SteamApps, then download anything missing.
I did exactly as above to the entire contents of the SteamApps folder when I upgraded my computer, and everything worked flawlessly.