Server 2008 64 bit standard member server on a domain

can you install any other software?
is the Installer Server running?
are DCOM settings correct?
are you doing a right click RunAs?

Try this:
Download the latest Windows installer for the OS
Install it
Execute Symantec Antivirus.msi - If the error still appears then proceed further.
Click Start - Run - cmd
Type msiexec.exe /unregister ---enter
Type msiexec /regserver
Execute Symantec Antivirus.msi - Installation should be successful.

did you try this?
http://service1.symantec.com/SUPPORT/ent-security.nsf/ppfdocs/2009082520222348?Open&dtype=corp&src=&seg=&om=1&om_out=prod

I have checked all these settings> they are OK.
Except for this method>

Method 5: Fix the broken security key for the MsiServer service
1. Click Start, click Run, type regedit.exe, and then rename the following key to Old_Security:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSIServer\Security
2. Restart the computer (you must do this).

3. Run Instmsiw.exe for installer 2.0 again; this corrects the broken security key for the MSI service.

Under MSIServer\Security  "I do not have a "Security" KEY so there is nothing for me to rename.
thanks
aa

k.  lets verify if it's the MS Installer or SEP.

are you able to install any other software?

I was able to install Belarc advisor
removed and installed the new version no problems.

aa

have you tried downloading the SEP file again?  it shouldn't fix the issue but it can't hurt.

When you say SEP File you mean setup file?
Thanks
aa

sorry, yes, the Symantec  Endpoint Protection installer.

Hey Thanx for the help I , was able to figure out the problem
c:\windows\system32     regserver
and
c:\windows\SysWOW64  regserver  this one did it for me

Thanks

Thanks for the help
aa