Migrating Outlook 2010 autocomplete file from one computer to another.

Comparing to Outlook 2007 there is no such thing like nk2 file in Outlook 2010.
The equivalent file called "Stream_Autocomplete*.dat" and located under

"C:\Users\%username%\AppData\Local\Microsoft\Outlook\Roamcache"

So if you want to migrate or transfer autocomplete settings to another computer just copy the above file over and name it as per similar file on the target computer.