If you're a hardware geek who absolutely must know every bit of information about your PC and attached hardware, including performance statistics, then Dr. Hardware ($30, 30-day free demo/trial with feature limitations) may well be for you. This program gives you an almost mind-boggling amount of data, including very in-depth and detailed benchmarking of your CPU, memory, video subsystem, hard disk, and more.
For a start, Dr. Hardware offers a comprehensive list of your PC's base hardware, listing the capabilities of each, including vendor name, when available. There's also a CPU performance monitor that tracks your CPU's performance. If you have a multi-core PC, it shows the performance of each individual core.
All that is just the beginning, though. Dr. Hardware then offers more in-depth looks at each piece of hardware, track system resource usage, display information about your software, and more. Many people will also welcome the benchmark section that runs a series of tests on your hardware, and compares its results to other hardware. Note that not all features are enabled until you register. For example, the trial/demo version won't measure your system's temperature, fan, and battery voltages.
There's really only one drawback to Dr. Hardware: its price tag of $30. True hardware geeks may want to pay, but casual users who just want to get a better understanding of what's under the hood of their PC will probably find the price too steep.