MS-Outlook 2010 keeps opening automatically

I am receiving a very annoying problem that involves MS-Outlook 2010. I never use this program even before.
Just recently, it started to open automatically.
I can’t seem to locate the cause why it keeps opening.
There are times that I have to leave the computer for a while, and then when I go back, the Outlook window is on again.
This happens randomly.
Sometimes it will open after few hours of using my computer, sometimes it will open after few minutes of starting my PC.
How can I fix it?
Where can I set the settings for this to stop reappearing?
Help me.
Thanks.
