SysGauge - SysGuage is a responsive software utility that monitors the memory status, CPU usage, as well as network and disk activities of your system.
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
Big Meter Pro - Big Meter Pro is a utility that monitors the disk and memory of your CPU.
TreeSize - TreeSize tells you where precious disk space has gone to.
SSuite System Monitor - SSuite System Monitor is a completely portable and stand-alone application that monitors the RAM of your system, page file load, CPU usage, and the system power in real-time.
SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.