For those who get this error, It is because you are not using Steam. I'm seeing multiple people here posting that this is a bug, but it just means you are using the old version of Half-Life with the WON Version. I can be wrong with this, but I am seeing now multiple threads with the TrackerUI Error that leads all that the person is using WON.

Steam is required to play this Open Beta. Click This Link (What is Steam) and look in the right, and click "Free Download". Once you downloaded, install Steam, and register an account. Once done, go to "Game --> Activate game" in the Steam Program and use your half-life serial key to activate your account completely in order for you to download Half-Life for free.

Bir başka yerde de bunu buldum saat geç oldu çevirebilirseniz bakın arkadaşlar yoksa yarın akşam yardımcı olurum.