Sensorsview is a temperature and system monitor that displays the information in the notification area of the taskbar. It is motherboard dependant so check the read me for compatibility but it covers most of the popular ones from what I can gather.
It measures:-
CPU temp
HD Temp
Case temp
Fan speeds
Voltages
http://www.majorgeeks.com/SensorsView_d4859.html
Install as usual, copy the folder to another location minus the uninstall.exe then uninstall the original. Space is an issue for me so I have also been able to delete the folder 'drv' from the install and the program still runs taking up a little over 300kb
NB This is a freeware versions but there is also a Pro version for $19.95