Final answer:
To check Windows Update history, Kevin needs to view the DataStore.edb file located in the SoftwareDistribution folder of the Windows directory. This database contains the detailed records of Windows Updates on the machine.
Step-by-step explanation:
To investigate the Windows Update history on a Windows machine, Kevin needs to check the DataStore.edb file. This file is a database that stores all the information related to Windows Updates, including what updates have been installed, when they were installed, and whether the installation was successful or not. It is located in the \DataStore subfolder within the \SoftwareDistribution folder, which itself is located in the Windows directory (typically C:\Windows). The other files mentioned, such as contacts.edb, Windows.edb, and WLCalendarStore.edb, do not store information about Windows updates.