1) Open an elevated command prompt.Go to the Start Menu and find command prompt, then Right-click on it and select 'Run as administrator'
2) Type in "fsutil behavior set disabledeletenotify 0" and hit Enter.
To disable it just type "fsutil behavior set disabledeletenotify 1" and hit Enter.
Its really that easy! If you're using an SSD there's no reason not to enable TRIM as it gives you a tangible performance increase.