The Open Hardware Monitor is a free open source application that monitors temperature sensors, fan speeds, voltages, load and clock speeds of the hardware of a computer. It runs on 32-bit and 64-bit Microsoft Windows operating systems using the Microsoft .NET Framework. Linux systems with Mono are supported as well, although the available sensors are (currently) very limited.
Fixed support for more than one Nvidia GPU on x64 systems.
Tools and Utilities
Product page: here