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 follow these steps
1. Copy your NK2 file into the following location c:\Users\%username%\AppData\Roaming\Microsoft\Outlook making sure it has the same name as your outlook profile.
2. Click start and type in the search box outlook.exe /importnk2 and hit enter.
Outlook will start and import the contact into the new suggested contacts