Hi,
Possible Cause :
This is mostly due to insufficient permission to gain access to a key in the registry.
Possible Solution:
Open registry editor as an Administrator
Go to the location "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-18\Components"
Right click on the key C9AE13788D0B61F80AF18C3B9B1A1EE8
Select Permission
Add the username with which SEP is being installed
Give Full Permission to this user
Click Advanced
Clear Inherit from parent the permission entries
Copy all the permission entries when prompted
Check the box to replace the permission entries on all child objects
Click OK twice
Restart the computer to take effect
Check this article as well
http://www.symantec.com/business/support/index?page=content&id=TECH135922