The NK2 files on your Windows 7 computer are used for the Microsoft Outlook program. When these files aren't working properly, you will not be able to send or receive e-mails. Fixing your NK2 files is not very hard when you employ the Windows 7 file checker. This is a program that is built into your Windows 7 operating system. The program will scan your computer files and repair any broken or corrupted files with correct versions.
Click on the "Start" button and then go to the "All Programs" menu.
Click on the "Accessories" button and then right click on the "Command Prompt" option from the menu.
Choose the "Run as administrator" option from the menu and type your administrator password into the field provided.
Type "sfc /scannow" into the command prompt and press the "Enter" key.
Wait for the program to fix your NK2 files and any other system files that are broken or corrupted.