I am finding my this 2 year old PC with Windows 7 needs a defrag now more often than in the past, perhaps more than once a week. Otherwise it takes ages to close down, maybe I even have to switch off the power. Although the analysis does not show a defrag is needed.
I use Windows Disk Cleanup often along with a multiple cleaner available with AVG. The only programs showing in my startup are AVG, Adobe updates and Realtek Sound manager. CHKDSK failed to show any problems to correct,
Someone has suggested Windows 7 Defrag makes considerable use of the drive but now serves little purpose. Yet it must have some use in defragging otherwise presumably it would manage to speed up closing Windows for awhile.