Before following instructions below, be sure to have the newest .NET Framework, DirectX and Microsoft Visual C++ Redistributable Packages updates installed. 

Also be sure to have GTA IV 1.0.7.0 installed (wich you can download here: http://goo.gl/JJsXe7) or EFLC 1.1.2.0 installed (wich you can download here: http://goo.gl/lpdhpI).


BEGINNER INSTALLATION INSTRUCTIONS:
First you need to know where your GTA IV/EFLC main folder is. It's usually in one of these paths:

GTA IV 1.0.7.0
Retail version: C:/Program Files/Rockstar Games/Grand Theft Auto IV
Steam version: C:/Program Files/Steam/steamapps/common/Grand Theft Auto IV/GTA IV

EFLC 1.1.2.0
Retail version: C:/Program Files/Rockstar Games/EFLC
Steam version: C:/Program Files/Steam/steamapps/common/Grand Theft Auto IV Episodes from Liberty City\EFLC

When you've found it, simply extract all the files from the _Install folder to your GTA IV/EFLC main folder.


If you need further help, contact me here:
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And i will try to help you out personally.