MHDD - MHDD is the most popular freeware program for low-level HDD diagnostics.
SpeedFan - Hardware monitor for Windows that can access digital temperature sensors located on several 2-wire SMBus Serial Bus. Can access voltages and fan speeds and control fan speeds. Includes technical articles and docs.
CrystalDiskInfo - CrystalDiskInfo. A HDD/SSD utility software which supports a part of USB connection and Intel RAID. >> Download. Intel RAID (IRST). IRST 11.
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
HDD Regenerator - HDD Regenerator is a unique program for regeneration of physically damaged hard disk drives.
smcFanControl - [Download] smcFanControl 2.