chrisvu22

you have a bad data file in your save folder

go to your start menu, type run, hit enter, then type %appdata% enter then go to local, rockstargames GTAIV and delete whats inside the save game folder. if you are using Xlive.dll this folder will be in documents rockstargames, save games

You need to launch GTA IV as administrator.

To do this, right click on the shortcut and click on Run as administrator.

Please use the search feature on the site before posting.
1) Make sure your GTA directories are not readonly, especially the COMMON and DATA folders.
2) Also ensure you are running the installer as an administrator.