Source Engine games are Half-life 2, Team Fortress 2, Counter Strike Source and others. Those games, or better part of those games, can get internally defragmented and can’t be optimized using a software that defragments Windows
hard drives. It is a good idea to defragment those games regularly to speed them up.
You need a software called GFCScape to do this. It’s just a small application that requires the Windows .net Framework 2 to run. Run GFCScape after installing it and click on File > Open in the menu. Navigate to your steamapps folder on your hardrive and select one of the files in the list.
All games benefit from defragmenting the files starting with source 2007 while defragmenting the files named like the games benefit only those games. GFCScape will load the file and display information about its contents. Click on View > Columns to add the Fragmentation column to the menu.
Every value greater than 0,0 means that the file is fragmented and will benefit from defragmentation. To be able to defragment the files you need to enable Write Access which can be done in Options > Write Access.
I had to load a new file afterwards to be able to defragment it. To start the defragmentation of the files click on Tools > Defragment. This should only take a matter of seconds and display the fragmentation score of 0,0 after loading the game again.
This way you are able to fragment games like Counter Strike Source, Half-life 2 and Team Fortress 2 resulting in a speed up.
Read More: GCFScape Download
Speed up all Source Engine Games 
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