Outlook 2010 does not use an NK2 file anymore to store suggested contacts instead it uses a file called Stream_Autocomplete.dat located in C:\Users\%username%\AppData\Local\Microsoft\Outlook\RoamCache, this means you can’t copy the NK2 file from one machine to another when upgrading.
What you need to do now is import the NK2 file into suggested contacts to do this […]