I have been using Avast Pro for about 3 months and noticed since using Avast, Perfect Disk tells me that $Secure:SDS is always fragmented at start up. When Avast is uninstalled it dosent happen. Why does Avast cause this???
Some discussion of C:|$Secure:$SDS:$DATA can be found in http://forums.pcpitstop.com/index.php?showtopic=154652#
Conslusion:
It's either 'Secure Data Storage' or Secure Data Service'. I wouldn't be too worried about defragging it.