If the AV hasn't been turned off before starting the vCenter 6 installation, you'll probably end up with its services running, but no installation to uninstall (the AV would probably have had blocked some important installation scripts).
Of course, this "installation" won't work so we have to reinstall it; however, if you try to do it just by running the vCenter 6 install .exe again, you'll get an error saying that the needed (default) ports are already in use.
To overcome this, stop all VMware Services (usually stopping the vCenter Configuration Service along with vCenter Server service does the job - it stops all or almost all other running VMware services).
In the end just (re)run the vCenter installation again - if you still get any errors (about ports already in use), just allow the system a few more minutes (to unload all the services completely).
Note: you can take a look at which service is using which port by running the netstat -aon | more command.