Antivirus software is often the enemy of pentesting, because most useful tools (Cain, and even NetCat) are detected as "Potentially Unwanted Programs".
Some antivirus are easy to disable (like stopping a service), others are a real pain (non stoppable drivers). Symantec Enterprise 10.2 with anti-tampering options belongs to the second category.
Symantec Antivirus can be removed from the "Add/Remove Programs" Control Panel menu. However it asks for a password on removal.
This password is not a product feature, but a feature of Windows Installer subsystem. Therefore it is very easy to bypass. First step is to attach a debugger (like OllyDbg) to the MsiExec.exe process the password window is belonging to (this requires Administrative rights or Debug priviledge).
Second step is to set a breakpoint on GetWindowTextA. Then run the program, enter any password, and the breakpoint should be triggered. From that point, step out a few times until TEST AL, AL is encountered.
Setting AL register to any non-zero value allows product uninstall.
Note: ECX and EDX registers point to (entered and expected) password hashes. But this is an other story :)