To watch a demo that you recorded go into console by pressing the tilde "~" key on your keyboard. Then type "Playdemo NAME" without the "Quotes" you will need to wait a few seconds for the demo to load.
Locating the demo
Counter Strike Source
- To locate the demo you recorded you'll need to go into the cstrike folder of counter-strike:source. Go to "C:\Program Files\Steam\steamapps\Login Name\counter-strike source\cstrike"
Team Fortress 2
- To locate the demo you recorded you'll need to go into the tf folder of team fortress 2. Go to "C:\Program Files\Steam\steamapps\Login Name\team fortress 2\tf"
To record a demo see
How do i record a demo in tf2 or cs:s.