The 23rd piece of enemy intel can be found in the mission One Shot One Kill.

This secret is only accessible during the final fight with the Russians at Pripyat. Get the ferris wheel behind you and useing your compass look east. You should be looking at a horrible apartment building. Go towards it and look for a hole in the fence. Notice a closed door to another crappy Russian dwelling to the compass' Southeast.

Past that door is the laptop. The door can be opened by walking further down the map to another of these doors. This is where the enemy soldiers usually spawn. To keep the game realistic, they will not spawn there when you are looking and will therefore spawn somewhere else, which is at the intel's location. This will open the door to let the enemy soldiers enter the battlefield.

[ Register or Signin to view external links. ]

If you need any help PM me.