1)   Performance Monitor 3.8.5
Monitor your CPU, Memory, Disk and Network utilization with this very useful program

 2)   Stellar Smart - Monitor Hard Drive Performance 2.2.1
Stellar Smart - A Hard Drive / Disk monitoring software to diagnosis and monitor the activity of Hard drive as Temperature, Head Flying Height, Spin-Up Time.Stellar Smart acts as an "early warning system" for pending hard disk problems.

 3)   FreeSpacePro V4 4.0.0.0
FreeSpacePro V4 is a disk monitoring utility that allows you to monitor free space on all your hard disks. It is bundled with a drive clenaer utility that allows you to find specific (large or old) files and move, delete or shred them.