What do you mean "without having to start it", you mean at boot-up, or does
it close by itself and you have to restart it? If the latter is the case,
I'd say you have a problem.
If the first, simply create a shortcut and place it in the
Start>>Programs>>Startup folder. You can right-click the Outlook icon on the
desktop and choose Send to... Create shortcut; the shortcut should be
created on the Desktop. Right-click this new shortcut and click Cut. Now
right-click the Start button and click Explore All Users, and expand the
Programs folder and click on the Startup folder. On the right pane,
right-click and click Paste.
Now, after all this is said, and not yet done, being that Windows needs a
lot of resources and it is very hard drive intensive at boot up trying to
load all the services and background apps like antivirus, etc., to run an
application like OL at boot up is not in the best of its interests.