How do I run Endpoint Protection at startup before anything else loads

I don't know how but I recently got infected with a bunch of trojans and other viruses.  I am in the military and was able to download Symantec Endpoint Protection for free for my laptop.  My computer is running so slow and it takes like a whole day for the scan to complete.  And when it does complete it deletes some of the viruses but a lot says that it can't be deleted because the file is in use.  And the ones that do get deleted seem to come back after I restart my computer.  I tried selecting the option to run at startup but all that does is run the scan after everything has already loaded.  I have used other scans in the past that give you the option to run the scan immediately when windows starts but before everything else has a chance to load.  Does Symantec Endpoint Protection have this option and how do I do it.  And if not can anyone recommend anything to help me use this programs to get rid of the viruses completely.  Thanks in advance.