Pad - LOCK icon in Upper Right Corner of Screen - How did it get there??

When I start my Mac (G5-10.4.11) for the first time I have an icon of a pad-lock in the upper right hand corner of my screen and appears in the 'closed or locked' position. I don't know how it got there. I think it has something to do with 'Keychain' but not sure. When I open Entourage (2008) to check my email for the first time following a boot sequence, Entourage asks me for a keychain password and after entering the password, the pad-lock icon in the upper right corner now indicates an 'open' or unlocked condition. I don't have to do this again as long as my computer stays on. I've tried changing the access setting in Keychain to 'ignore' Entourage and Keychain but it still asks me for a keychain password following a re-boot. What did I do to get the pad-lock icon there in the first place? And, how can I turn OFF that 'pad-lock' and not appear on my startup screen? I have another hard drive in my computer that I boot from occasionally and the "pad-lock' icon does not appear on my startup screen and I can check Entourage without entering any keychain password. I really don't need password protection on my home computer, it's very annoying every time I check my Entourage email.
Thanks,
Bill