I'm having trouble with VAC.

Valve's Anti-Cheat system (VAC) is automatically detects programs and other methods used to cheat in Valve's games. If your account has been banned for past cheating violations, VAC has detected that someone using your account used an illegal cheat while connecting to a secure (VAC-enabled) server.

If VAC has determined that your account was used to cheat, you will be banned for one year from playing Valve's games on VAC-enabled game servers. However, you will still be able to play on game servers that are not VAC-enabled.

Under no circumstances will we unban an account that was detected cheating. Even if someone else was using your account when the cheating took place, you are responsible for ensuring that your account is used in accordance with Valve's anti-cheating policies.

In the extremely unlikely event of VAC erroneously banning innocent players, we will automatically unban all affected accounts.