Office 2010 Outlook - Navigation Pane Folder Options

I am running Windows 7 (Home Premium 64b) with Office 2010 (Home & Bus) on our new desktop PC. Just finished installing both without problem. Have now turned to adding email accounts to Outlook. I added 4 POP3 accounts, using the wizard. The wizard's test mails - and my own independently sent test mails - have confirmed that send/receive work fine in all 4. One of the 4 has been selected as my default account.

All 4 accounts show up in the navigation pane on the far left of the screen. The default account appears at top, with a black arrowhead to the left of its name. Under it appear the standard list of system-offered subfolders: Inbox, Drafts, Sent Items, Deleted Items, Junk Mail, Calendar, Contacts etc. etc.

The other three accounts are listed below this array. Each of them has a white arrowhead to the left of its name. None of these accounts has any system-offered subfolders (Inbox, Sent Items, Deleted Items etc) listed under it.

Question -
How do I get Inbox, Sent Items, Deleted Items and the other system-offered subfolders to appear under these non-default accounts in the Navigation Pane? For example, I know (from viewing the same accounts independently on my laptop) that these non-default accounts are receiving mail; however, I cannot view any of this mail because the Inboxes of these accounts are not accessible from the Navigation Pane. I would like all 3 non-default accounts to at least show Inbox, and - if possible - one of them to also show a fuller menu including Drafts, Sent Items, Deleted Items, Junk Mail etc.

I have looked everywhere in Outlook there is, but can't seem to find the path to the fix (or - if I have found it - I guess I am not recognizing it).