Auto archiving and personal storage folder (.pst) in Outlook can become an issue, and in the event you need to turn these off, follow these steps and you'll be all set. Below are the instructions for Outlook 2007:

1. Close all open programs
2. Click START | RUN and type in REGEDIT
3. In the registry browse to ComputerHKEY_LOCAL_MACHINESOFTWAREMicrosoftOffice12.0Outlook
4. Create a new DWORD value: DisablePst with a value of 1
5. Close the registry

When you open Outlook PST usage and auto-archive will not be available.