QWatch

QWatch is "a little tool to show how much memory/space/cpu you have free.
The program appears as an icon in your system tray, click it and a window displaying the information will appear. The program takes no cpu while the main gui is hidden and even when it is shown it takes very little system resources (about 2 Mb ram and 0% cpu on an 1.6 Ghz).
The program supports drives and ram up to 1024 Tb and unlimited numbers of cpus." With version 2.0 it became skinnable.ยด´