HWMonitor is an old favorite, a simple tool for monitoring system temperature, voltage, fan speed, and other factors. It's portable freeware that runs when you click it, needing no installation, so it can go on a USB drive and run on any PC. It's extremely compact, too, at less than 400 KB. It's been through regular upgrades over the years; the latest version, HWMonitor Pro, adds a Graph Generator and the ability to remotely monitor other PCs via the Internet, among other improvements.
HWMonitor opened with an expanded tree view of our system's voltages, temperatures, fans, CPU core temperatures, and the drive, airflow, and assembly temperatures of the main hard drive, with every other line highlighted, like a spreadsheet. File, View, Network, and Tools menus let us save monitoring and SMBus data; edit selections; enable the network Listening Mode as well as open and close a connection to an IP address or ENUM network; start and stop the log; and set options such as Fahrenheit or Celsius and the log path. One especially cool feature is the ability to add any of the monitored values to the system tray in the form of a tiny display by right-clicking it and selecting Add to Tray. The Graphs Generator automatically creates graphs for each logged session when you stop logging data and saves it in a folder the program creates automatically in the user-selectable log folder. We started the log and stopped it, and then opened the folder containing the graphs. These were quite readable and even attractive. We could set the graph size from the Options dialog as well as opt to generate a second set in a different size as well as a CSV file. The online Help and documentation offered clear explanations and screenshots. However, HWMonitor is very easy to use; in fact, it does the hard part for you by automatically detecting compatible system sensors.
HWMonitor only tracks components that have compatible sensors, which depends on your brand and model of motherboard, processor, and so on. The ability to monitor remote machines with ease sets it apart from other free hardware monitors, though. It's well worth a look.