The tool is there for you during the editing handling.dat easier.
It's compatible with the latest Version of GTA IV 188.8.131.52.
It supports also four different languages like german, spanish, italian and russian.
I translated it with google so sorry if there are some misstakes.
Downloadlink: Click here!
For all XP users:
If an error pops up, like uxtheme.dll is damaged. You will need this: Click Here!