Make program instantly start up when login. c#

I have previously posted a question about this but I did not get an answer that suited my needs, so maybe I need to be more specific?

I am trying to make my program instantly start up when the person logs in. It is a computer locking device so I need it to start as soon as possible. I know this is possible because anti-virus programs do this. Such as ESET or Avira.

I currently have my program entering a key into the registry to enable it to start up when the user logs in. But I need it to be much more 开发者_运维百科efficient to maximise security.

Any help would be appreciated, Thanks.

---

Actually, most anti-virus programs run as a windows service. If you need instant on then that's the only way to go.

The part you see starting after log in is simply the UI for those services.