Symantec/Norton Live update are responsible for BSOD ( Blue Screen Of Death )
for millions of PC in China
see story
http://www.computerworld.com/action/article.do?command=viewArticleBasic&articleId=9019958
It is a sin to recommend Symantec to you.
You should use spybot.
Spybot-Search & Destroy (Spybot-S&D) is a popular malware,
spyware and adware removal program, which is free.
http://www.safer-networking.org/
Spybot-S&D can fix problems with system internals (Registry),
Winsock LSPs, ActiveX objects, browser hijackers and BHOs,
and can to some extent protect a user's privacy by deleting
usage tracks like tracking cookies.
Spybot also includes an "Immunize" feature to block the
installation of spyware before it occurs
e.g. by modifying the hosts file.
Another tool included in Spybot is a file shredder,
for the secure deletion of files.
Spybot is not intended to replace anti-virus programs,
but it does detect some common trojans.
Spybot-S&D also recently added an anti-rootkit function.
The Spybot TeaTimer module can be optionally enabled,
providing a level of active, real-time protection
from undesirable registry changes. Spywares and virus cannot
install itself behind your back.
I use Avast and spybot because they don't conflict with one another.