Power supply fan and system temperature
From the graph, you can see when I discovered the power supply fan stopped and I opened the window, and when I shut down the computer to replace the failing power supply. When the computer came back up with the brand-new Silverstone SST-40F, CPU temperature dropped by 6 degrees.
Unfortunately, the Maxtor also failed without any warning, and this is now the second (or almost the tenth, depending on how I'm counting failures) time the Maxtor has failed. Honestly, I am now completely disappointed with Maxtor.
From the graph, you can also see when I replaced the case fan (late Saturday), and when I swapped the failed Maxtor with a Seagate Barracuda drive mounted with Zalman ZM-2HC1 (between Saturday and Sunday).
The CPU temperature increased a few degrees after replacing the failed Maxtor; I don't know whether it is because the Seagate is hotter, or whether the heatpipes successfully transferred some of the drive's heat into the air inside the case. According to smartctl, the Seagate is 46 °C.
If you look at the MRTG “yearly” graph you can see when my power supply failed approximately the same time this year (end of October / beginning of November); at that time the CPU temperature went up to 56°C before the machine started resetting itself and trashing all the data in the Maxtor.