As you know, XP has the ability to have your browser and email client of choice on the start menu (top 2 items). If you set the start menu to use Outlook, when using that icon, it forces the user to the inbox. In Outlook (2k and XP) you have the choice to change which folder Outlook will open up to. WIndows XP over rides that setting. Therefore, if you have set Outlook to open to "Outlook Today" and you click on the WinXP-generated Outlook icon on the start menu, you will open in the "Inobx" not "Outlook Today". There's a reg entry that forces it to the inbox. By removing a parameter, the normal outlook setting will work. The key is at:

[HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Microsoft Outlook\shell\open\command]
@="\"C:\\PROGRA~1\\MICROS~2\\Office10\\OUTLOOK.EXE\" Outlook:Inbox /recycle"

By removing the 'Outlook:inbox' parameter, Outlook will open in the correct folder that you chose.