How in hell Symantec livereg and liveupdate got to my system???

I got infected with some Trojan.Vundo last week which McAfee AntiVirus
Enteprise 8.5i Anti-Spyware patch was able to fix. I am surprised to
see some Symantec LiveReg and Symantec LiveUpdate in my XP Pro SP3's
"Add or Remove Programs." How in hell Symantec stuff got in my system?

My company tried the Spyware Doctor but it can't even whack the
Trojan.Vondu. After I installed all XP workstations' McAfee AntiVirus
Enterprise 8.5i patch 4, patch 5 and Anti-Spyware, the Spyware Doctor
was tagged to contain spywares and other potentially unwanted
programs. So far so good the McAfee Anti-Spyware was able to clean up
all computers with all sort of internet parasites, trojans, etc....