Man, Grand Theft Auto IV is so tempting...but I don't want to support a shit port.
I'll just say - GTA4 PC has majorly improved from what it was before, since they improved Shadow performance AND now that Rockstar Club is built DIRECTLY into GTA4 itself, instead of being a separate program. Runs much better - also, I am running latest NVidia drivers, as well.
You'd still have to activate Securom, too.
Plus, GTA4 PC runs w/ G4WL, as well.
Keep also in mind - 15 GB is a HUGE DL.