Previous versions of Outlook used an .NK2 file to store the auto-complete cache however Outlook 2010 now stores this information in a .DAT file, namely Stream_Autocomplete_XXX where XXX are a string of HEX. To move this .DAT file;
1. Close Outlook
2. Browse to C:\Users\%Username%\AppData\Local\Microsoft\Outlook\RoamCache.
3. Find the file with the latest date modified and copy to removable media.
4. On the target machine, paste the file to the same directory.
5. Launch Outlook to confirm the transfer has completed successfully.