In Outlook 2013, the format of the autocomplete file is changed from nk2 to dat. You need to run a command to convert the file format.
First, locate the old nk2 file in Outlook 2003:
For Outlook 2003/2007 with Windows 2000, Windows XP, or Windows Server 2003:
C:\Documents and Settings\[User Profile]\Application Data\Microsoft\Outlook
For Outlook 2003/2007 with Windows Vista, Windows 7, or Windows server 2008:
Second, locate make a copy and then copy it to the Outlook 2013 file path:
For Outlook 2010/2013 with Windows Vista, Windows 7, or Windows server 2008:
The name of the NK2 file is in the following format: Stream_Autocomplete_X_AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA.dat The X is the file index (usually 0) and AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA is a random 16-byte key in hexadecimal format.
For Outlook 2010/2013 with Windows XP:
C:\Documents and Settings\[User Profile]\Local Settings\Application Data\Microsoft\Outlook\RoamCache
Third, download NK2Edit. Download the zip file and you don’t have to install it. Open 2 instances of it for the NK2 file in Outlook 2003/2007 and the dat file in Outlook 2010/2013. Backup the NK2 and dat files before proceed.
Fourth, copy all records in NK2 in NK2Edit and paste them into dat also in NK2Edit and save and rewrite the dat file.
Reboot computer if it’s necessary.