Find any and all copies of the file AeXAgentUtil.exe and from each location
a. Run AeXAgentUtil.exe /uninstallagents
b. Aexnsagent.exe /uninstall
(Both executables are located, by default at: C:\Program Files\Altiris\Altiris Agent\)
Open Registry find keys where old agent path(s) is found and delete those registry keys
a. This Includes two entries under the Windows Uninstall registry that could still exist (don’t forget the wow64 hive as well) “Altiris Agents” and “NS Client”.
b. The Altiris Agent is under the uninstall key and NS Client is under the Altiris\Express key both need to be deleted if not already deleted by the /clean.
HKEY_LOCAL_MACHINE\SOFTWARE\Altiris\eXpress\NS Client
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall\AltirisAgent
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\AltirisAgent
c. As well you need to clean any references of the Altiris Agent on
HKEY_CLASSES_ROOT\CLSID
HKEY_CLASSES_ROOT\Typelib
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Clsid
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Typelib
Reference
How to remove the Symantec Management Agent (Altiris Agent) manually on the SMP server and assign it to a new drive http://www.symantec.com/docs/HOWTO77405