Good software for measuring computer temperature?
What is the best lightweight temperature monitor for windows 7?
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I don't use Windows, but my brother swears by Speedfan: http://www.almico.com/speedfan.php
(It has other features as well, most notably being the ability to monitor and alter fan speeds.)
I use EVEREST (Lavalys, Ultimate Edition, payware) for on-demand temperature monitoring (Mobo, CPU, GPU, HDD) and much more. It can log the data to a file or you can keep it running in the taskbar notification area (with separate icons for each component temperature), and it consumes very little resources.
Speccy (Piriform, freeware) is also a nice app to monitor temperatures (and more) on-demand. I happen to use ATI Tray Tools (or RivaTuner) for my 24/7 GPU temperature monitoring, which also gives me a good idea of the general temperature inside the case. I'm using Windows 7 x64.