Symantec Client Security cannot be used on a server class OS. Please install Symantec AntiVirus instead.
This is just because of old version of symantec residing on your computer. Even when while unstalling it will give the same error. Follow below steps :
1. In Add or Remove Programs select Symantec Antivirus, and then click Change.
2. Select Remove.
Symantec will be uninstalled. :)
3. Delete all symantec related folders from Program Files, Common Files and Documents And Settings.
4. Try the installation again.
5. It will work. Atleast it worked for me.