Symantec Silent Removal
There are a number of articles on removing Symantec AntiVirus silently. There is a link to thread on avoiding MSI uninstall reboots. There are good suggestions and some bad. Mostly it's simple. Cleaning up SAV w/o a prompt, password, or user-required action is a little non-trivial.
Someone else did the heavy lifting. You must instruct Symantec to ignore the uninstall password, and that is easily accomplished via a reg-hack. However, reghack via GPO is a PITA. Google turned up: Policy Maker (Registry Extension). This is not news. NEWS is that it farking crashes as soon as you try to use it. Well, it crashed if you have IE7 installed.
Ironically, perhaps, you must update the registry to make this work. Specifically you must disable object caching in IE7 for mmc.exe. (This is too precious). Microsoft Article (which OUGHT to be LINKED from the Webpage of the tool, or included in the installer, given how long IE7 has been out) #938611 - GP Snapin Crash fix.
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_OBJECT_CACHING] @="" "mmc.exe"=dword:00000000