Looks like Rockstar have released a small game update for the PC version of GTA IV. Next time you log on to Games for Windows LIVE you'll be prompted to download it. The update includes everything from the previous patches, so if you don't already have the 1.0.3.0 patch you'll only need to install this one, not all of them.

Rockstar haven't yet added this to the official site yet, so we're not sure of the exact details of what it does. However, some players are reporting performance increases with an extra 5 fps, sometimes even more. Guess it all depends on your setup. Let us know in the comments how the patch effects your game. We'll post full details of the changelog once Rockstar put it up.

UPDATE: It's simply a maintenance update:

Maintenance Update:

* -Resource management adjustments based on the operating system detected.

As an aside: Both ATi and nVidia this week released updates to their graphics card drivers. These can of course also help give you better performing games, so it's recommended you upgrade these as well.

Links: ATi Catalyst 9.6 or nVidia 186.18 for the latest drivers.

EDIT: Local mirror of the patch here: download patch 1.0.4.0