for your Gaobot virus,
Removal using the Removal Tool
Symantec Security Response has developed a
removal tool to clean the infections of W32.HLLW.Gaobot.ADX. This is the preferred method in most cases.
Manual Removal
Perform a manual removal if you cannot obtain the tool.
The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
1. Disable System Restore (Windows Me/XP).
2. Restart the computer in Safe mode or VGA mode.
3. Reverse the changes made to the registry.
4. Update the virus definitions.
5. Run a full system scan and delete all the files detected as W32.Gaobot.ADX.