Disclaimer: This is only for those using Exchange (and always backup your registry before editing).
So you've hit Shift-Delete on a mail item or perhaps even setup a POP account on a system that totally drains all of your messages from your Inbox. Don't fret, highlight the folder in question, go to Tools > Recover Deleted Items... and bring your messages back from the brink of death.
What's that you say? You don't have Outlook 2007 with item recovery enabled on every folder. Well here's the fix for those with older versions of Outlook:
1. Fire up Regedit (Start > Run... Regedit, OK)
2. Locate and then click the following key in the registry:
3. On the Edit menu, click New > DWORD Value, and then add the following registry value:
Value name: DumpsterAlwaysOn
4. Close Regedit
You're done. Now you can retrieve items at will.