I have successfully transferred "Killing Floor" from my brother's laptop to my own via external hard drive. The problem, now that I have all the files, is that I don't know how to launch the game through Steam. All I did was copy files from his Laptop to the hard drive, then from the hard drive to my laptop, then I put the files in the "Steamapps" folder under "Steam" in my laptops hard drive. So the question is, how do I start up the game through Steam?
Steam supports backup-files. Here is a part from the Steam FAQ/How-To's:
Creating Backup Files
- Right-click the game in the Library section
- Select Backup game files...
- Check the boxes for any other games to backup at this time
- Click Next >
- Browse to the folder where you wish to create the backup files (the files will be stored in c:\program files\valve\steam\Backups by default) and click Next >
- Select the Backup file name and set the File size for the media you plan to use.
- Click Next > to begin the backup process.
- Once complete, choose Open backup folder to move or burn copies of the backup files
Restoring from Backup Files
- Install Steam and log in to the correct Steam account (see Installing Steam for further instructions)
- If the backup files were copied to a CD or DVD, the process should run automatically when the disc is inserted. If not, run steambackup.exe from the disc
- If steambackup.exe is missing, please download this copy of steambackup.exe and place it in the correct backup folder.
- Continue through the Steam windows to install the necessary games.
Alternative to the Backup Feature for Third-party Games
- Go to your \steamapps\ folder (by default, this folder is located at C:\Program Files\Steam\steamapps or on 64-bit systems, C:\Program Files (x86)\Steam\steamapps)
- Locate any .ncf files for the game.
- Locate this game's folder in the \common\ folder.
- Copy all of the .ncf files and the game folder to a disc or available hard drive for reinstallation
- For future installations, copy these files and folders to your new Steam installation.
- Make sure to place it back in the proper folder (\steamapps\ for .ncf files and \common\ for game folders). In addition you may also rename/delete your ClientRegistry.blob to force Steam to rescan your gamedirectory.
- Re-start Steam and you may see a small download to confirm the newly identified install.
For additional information read the complete article I linked below :)