Obscure System Tools

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CPUMSR v0.90 (Windows 2000 ~ Windows XP x86)
It is basically ThrottleStop, before ThrottleStop was released.

As it is nearly two decades old and was never updated after 2005, it would be a wise idea to not use this on newer processors, such as anything after Prescott-2M/Irwindale or Barton. Or, in simpler terms: don't run it on anything newer than a Pentium 4 or an Athlon XP.
[Download]

BatteryInfoView v1.23 (Windows 2000 ~ Windows 10)
A lightweight program that displays your battery's statistics, such as the wear, capacity, charge cycles, etc. I suppose that it is pretty good for what it does.

You know, I have always wondered if there was an English version of Yuryu's Battery Information 1.3 (YbInfo). I guess this program fills in that specific gap.
[Download]

hdparm for Windows (Windows 2000 ~ Windows 10)
Linux's hdparm ported to Windows, needs Cygwin to run. Nothing much to say about this particular progam.

A more compatible 'version' of quietHDD 1.5 build 250, as it is mostly guaranteed to run on Windows 10. I can't say the same for quietHDD, since it has been left untouched for nearly 11 years.
[Download]

ACFanControl v0.72ti (Windows 2000 ~ Windows 8.1)
Looks familiar? Yep, it's just a customizable TPFanControl. Be very careful when you are using this program though, as it is capable of causing softlocks or undesired side effects.

This is mostly a last resort option for messing around with an embedded controller, as Read & Write Everything v1.7 is known to be incapable of reading and writing to some embedded controllers.
[Download]

PCI-Z 2.0 (Windows XP ~ Windows 10)
CPU-Z, GPU-Z, and... PCI-Z? Whew, what's next? SSD-Z?

This program simply reads the PCI IDs on your machine, and then tries to accurately guess their actual names (e.g. 1292:FC02 = TriTech Pyramid3D). It's useful, if you do not know what exactly is residing in your machine.
[Download]

SSD-Z 16.09.09b (Windows XP ~ Windows 10)
They were not joking about this, seriously. Anyways, this is basically the 'CPU-Z' of SSDs.

Please note that this tool was no longer updated after 2016, so the accuracy and details may be lacking for newer SSDs. Still, it has quite a good amount of information that some might want or need to know.
[Download]