do you get any error..?

while starting the service?

Any smc.exe error..

try removing it from add/ remove programs, remove all the symantec folders. and try the install again.

 WHat exactly do you mean by run or run at start up?
are you not able to launch SEP client?
Scan is not running?
Are you getting any errors when starting SEP? or in event viewer-system or application log regarding sep ?

Check these discussions.

http://www.symantec.com/connect/forums/sep-client-services-unable-start-symantec-endpoint-protection-symantec-event-manager

we did not get any error.
it just we cannot open or run the SEP after installation.
we already uninstall it and reinstall again, but still it cannot be open or run.

Check the services needed to run SEP such as

Symantec Endpoint protection

Symantec Event Manager

Symantec Management client

Symantec Settings Manager

As to your condition it may be a virus issue or else a OS file corruption (assuming you tried all suggestions)

Try installing another client PC with SEP to test any installation errors and also try repairing the OS in the PC with issues.

Does this happen on multiple machines?
what was the AV used before?
Make sure the system does not have any infections before the installation
Check the event logs for any errors related to SEP.

If it is a single machine, try running clean wipe and then reinstall it.

What was the AV installed
before? Whether you uninstalled it properly before installing SEP?

Scan the pc with NSS in
safemode.....

Theres no antivirus installed before and our another problem is we cannot acces the safemode.
The PC keeps on restarting when we select the safe mode option.

Since there is no antivirus
previously there may be virus present in your system. Unable to boot in safe
mode also pointing in the same direction.. If possible connect this pc hard
disk into other pc which is having updated antivirus and scan .Then connect
back and see .If not possible to do in this way ,scan at least in normal mode..
You may also try the option safe mode with command prompt for scanning...

Use Norton Security Scan (NSS) to scan the pc, if you feel that SEP is not working.

I already know what causes the SEP problem. the PC is infected by sality virus.
can anyone help me on how to remove this virus...
please...

I think using the NSS tool makes more sense at this time. You can also try to scan this system from another machine that has the latest definitions.

You can map a network drive to the C drive of affected machine and scan from a different computer.

Aniket

i already scan through a map network drive, but tha SEp cannot do any action because it only map drive, it only detects the virus but the action is unchanged.
ill try the NSS tool. thanks

If you know the infected file names, you can try to delete them in safe mode with command prompt.

i already remove the sality virus but some of the files of the program is already corrupted resulting to not running of the application, so i decide to reformat the PC.

After removing the virus
whether you tried to reinstall SEP. If no try that. If not helps use clean wipe
tool to remove old entries which is created by sep and install sep once again

Instead of scanning via MAP Drive
Download the NSS tool and run a full system scan.
ftp://ftp.symantec.com/misc/tools/nss/

Then run clean wipe and install.

After tring the tool better run OS repair.

If sality virus is there it will corrupt the antivirus software at the time of installation.

Try SDAT tool to scan the system in command prompt which will delete the virus and later you can install the SEP.