I'm quite fond of munin and using it also at home to monitor my PCs. What was super-duper easy under Linux is pretty much unsolvable for me under Windows: I'd like to monitor CPU and Motherboard temperatures as well as fan speed.
On Linux I'm using lm-sensors and the plugin for munin was basically there.
But when it comes to temperature and fan speed I'm running against a wall. My research so far resulted in that Windows does not by default provide any out of the box ability to retrieve temperature/fan speed data. Third party applications are necessary which have knowledge how to communicate with the Motherboard chips.
The best I cam up with is that SpeedFan exposes a shared memory interface and there exists a library which hooks into Windows SNMP facility and bridges over to SpeedFans shared memory interface; it's called SFSNMP. Unfortunately the library doesn't work, there's a bug report at SpeedFan open about it, but it's currently not moving (although the SFSNMP author is active there).
So, unless that's going to work like anytime soon, are there any alternatives? I'm not found of buying any software to get that feature, given that I take it as granted that my system exposes me the information to properly monitor it, but anyway don't just not answer because of this.