Initially I have one account with one identity set up in my Outlook Express.
Now that I ADD another new account, with the initial account set as Default, how can I switch to the second account after running Outlook Express which loads the first account by default?
Thanks.I'm not sure if I understand you correctly.

Click on File -> Switch Identity and choose the other identityThere is only one identity, but two accounts.By SWITCHING, do you mean for retreiving EMAIL or sending email?  At the top of your OE, you should have a BUTTON called Send/Recv on the toolbar and it should a drop arrow on it's right side.  To receive email from an account other than the default account, click on the arrow and select the account from the list.  

You can also set any and all accounts to be included in mail retrieval any time you open OE or click on Send/Recv button.  To do this, go to Tools, Accounts, select the account, click on Properties, and check the box for "Include this account when receiving mail or SYNCHRONIZING".