Many of you might have well backed up and restored steam apps before and been successful. Its changed slightly ( Late 2012 ) and thought if anything, someone might well benefit from what I learnt. Steam decided all my programmes weren't installed and decided I needed to reinstall them and claimed I had 0mb hardrivespace left. Nice !
Some steam apps Use, *.gcf to store the main data, this is downloaded to ' Steamapps ' and extracted to common\'Gamename'
Some Create a directory in common these have no *.gcf file. Steam late 2012 now downloads content to 'Downloading', Then creates a folder in Common\'gamename' when download has finished and copy's data across to common\'gamename' and then patch's.
Backup: Your Steamapps folder often.
To restore from new, Thx to info from MmmBacon Steam forums.
Install Steam.exe and start steam once,log in account, ( DONT start any game installs ) then close steam.
Paste backup of 'Steamapps' folder, in correct location in Steam install location on hardrive ie C:\Program Files (x86)\Steam\Steamapps .
Load steam and Hit install of game, steam should detect files and verify and maybe patch if requied.
( Previous way of restoring backups was during downloading. You'd start steam download, close steam and replace the files from backup, steam would detect them and no more downloading would be required ) <--- Didn't work with Far Cry 3.
If you get the uninstall bug, Just backup you 'Steamapps' folder and any saves / what not and uinstall steam from the Steaminstall.msi and start from fresh, reinstalling steam. Unless someone has a fix this way the only way i found.
Other ways inc'd Deleting ClientRegistry.blob and AppUpdateStats.blob,
Moving steam install or game install to another Drive, these didn't work for me.
This might seem like to much info but i think it will help someone at some point.
Btw, I don't use the steam backup system as i don't like it.