Having used a pc for a very long time and being used to my pc freezing, I missed the hard drive activity light. Thankfully there is a freeware utility called Menu Meters which works for both Tiger and Leopard which does just that. So if you want to be sure your Mac is working, this utility is for you. It places indicators that you select in your top menu.
You can select any combination or all of the following:
- CPU (Graph or Percenage of each or combined cores)
- Hard Drive Activity
- Memory Usage vs. Available
- Network Activity