Clean AutoComplete (NK2) in Outlook 2010

For Outlook 2003, 2007

You able to found NK2 file in

WinXP: C:\Documents and Settings\<user>\Application data\Microsoft\Outlook

Win7: C:\<user>\AppData\Roaming\Microsoft\Outlook

For Outlook 2010....

There is no more NK2 file.
The actual file you are looking for is located is:


C:\Users\%username%\AppData\Local\Microsoft\Outlook\RoamCache\Stream_Autocomplete*.dat.


Deleting this file will not clear your AutoComplete list. 

Use one of the methods listed below to reset the Outlook nickname cache for Microsoft Outlook 2010.

Method 1

1. With Outlook 2010 open, click File (BackStage), and then click Options.
2. Click the Mail tab.
3. Under Send Messages, click Empty Auto-Complete List.

Outlook will generate a new nickname cache.

Method 2

1. Click Start, and then click Run.
2. Start Outlook by using the /CleanAutoCompleteCache switch.
   For example: Outlook.exe /CleanAutoCompleteCache
   Note If Outlook is not installed in the default location, you will need to point to the path of Outlook.exe.

Found it at this place http://aspoc.net/archives/2010/05/04/how-to-clear-the-autocomplete-list-in-outlook-2010/