Core Temp
Core Temp is a compact, no fuss, small footprint program to monitor CPU temperature. The uniqueness of it is that it shows the temperature of each individual core in a each processor in your system. You can see in real time how the CPU temperature varies when you load your CPU.
MemInfo
MemInfo displays the current memory usage of Windows in the system tray. With a small graphic and the value updated in real time, it gives a fast feedback to current memory usage in Windows.
Rainmeter
Rainmeter is a customizable resource meter that can display various performance data in different formats. It can measure CPU load, allocated memory, network traffic, NT performance data, uptime, free disk space and plenty of other stuff. The data can be displayed in a histogram, a bar, bitmap frames or just plain numbers.
Free HDD LED
Free HDD LED shows hard disk drive activity in real time. It monitors all physical hard disk drives connected to the pc (ide/sata/usb).
System Spec
System Spec is a self contained standalone EXE which can be run without installing. It lists a specification of your Windows PC without listing lots of useless memory address and unnecessary information.
GPU-Z
GPU-Z is a lightweight utility designed to give you all information about your video card and GPU.