The game is not moddable by default. You have to edit something before you can start modding.
Check this: http://www.gtaforums.com/index.php?showtop...entry1058714420
Seems the download is broken. Take this one: http://www.mediafire.com/?w4lj54pqxiocia6
Put the filelist.pak to pc/data folder and backup the old one.
Remove the read-only attributes from all GTA IV files and ensure you´re running it as admin.
Alternatively you can install XLiveLess. This post has been edited by NaidRaida on Saturday, Feb 25 2012, 07:39