How to remove Symantec Antivirus without using a password:
1. Open Registry Editor.
2. Navigate to the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\INTEL\LANDesk\VirusProtect6\CurrentVersion\Administrator Only\Security\
3. Change the value for useVPuninstallpassword key from 1 to 0.
4. Exit Registry Editor and now you can uninstall Symantec AntiVirus Client.
This trick should work on most version of Symantec AntiVirus client or Norton AntiVirus Client, including version 7, 8, 9 or 10.