XP SP3 Install Error - ftp.exe in use

When trying to install XP SP3, get an error about 10% of the way through saying that ftp.exe in use by another application.

ftp.exe doesn't show up in Task Manager as a running process so something else must be using it without ftp.exe showing up in the list somehow.

I get clean scans from Spysweeper, Adaware and Malwarebytes so I don't think this is because of a virus/trojan/malware.

I've tried killing all non-essential processes and stopping all non-essential services after a reboot and after disabling all network connections but the issue persists.

HALP! Plz and thanks.