Why do I have to use another client too?

[Lurkys302]

Really, why? It's silly.

:(

[Freyar]

What? APB hooks nicely into Steam, even if you're running it in a different location. If you want to port an existing install, install it via Steam, pause the download then kill steam. Copy the older content to Steam's folder under steam/steamapps/common/apb reloaded/

Verify the cache when you restart steam.