The Storage Team Blog about file services and storage features in Windows and Windows Server.
An observant Windows Vista user noticed a registry named NtfsDisableLastAccessUpdate under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem and asked us what this means. Last Access Time is a file attribute that’s updated when a file is accessed or otherwise touched. (This is often confused with the Last Modified Time, which is only updated when the file changes.) Last Access Time has a loose granularity that only guarantees that the time is accurate to within one hour. In Windows Vista, we've disabled updates to Last Access Time to improve NTFS performance. If you are using an application that relies on this value, you can enable it using the following command:
fsutil behavior set disablelastaccess 0
You must restart the computer for this change to take effect.
For more information about the Fsutil command and Last Access Time, see the Fsutil online Help.
Because there is no need for it to keep track of that information.