You need an asi loader for gta4 center asi plugin to run
GTA4CCasi.asi goes into gta iv game folder where other asi files are. 

gta4center.exe does not need installation, or deinstallation.
It dumps a settings file where you start it. your changes to shortcuts will
be saved into this settings file. If you want to revert to initial shortcuts,
just delete the GTA4CCData.xml file.

For a functiontest, you can also use the GTA4CCData.xml from this zip file.

cheers, and happy gaming.