Sharepoint 2003 authenticating with logged on credentials?

I’ll start by saying I am new to sharepoint, so please bear with me. Is there a way to have sharepoint use the logged on AD account for authentication? I am trying to create a single sign on environment where once users log into their PC they will be able to open up our company portal without being challenged for credentials. I’m not saying do away with the authentication mechanism, but make it seemless for users logging onto a PC with an AD account. I know something similar can be done in websphere, but as I mentioned… I am new to sharepoint. Any pointers in the right direction or documentation would be greatly appreciated. Any MS documentation I have found seems to be for using single signon for other systems such as a third party ERP system.

Thanks!