If you keep getting nagged for log ons when using sharepoint this will solve the problem almost 100% of the time. The trick is to use the Windows managed Stored username and password feature. To access this,
1. Simply go into Control Panel
2. Click User Accounts
3. Go into Managed Passwords and click Add
4. Type the URL of the server (without HTTP), for example portal.us.com
5. Enter your credentials and click Ok
Now anytime Windows attempts to access ANYTHING on this server it will use the use those credentials and your prompting issue should go away.
The downside to this is if you change your password, you need to remember to come change it here.