The hardware
I swapped out a Pentium D 930 (yes, I know, old hardware, but it served its purpose) with a Core2Duo T5500. Impressive! The motherboards are nothing impressive (read: I forgot the brand and model), and the only thing noting was the difference in memory: from 2 GB to 4 GB. Other than that, they are pretty similar in performance (I measured with 3DMark2006: 6500-ish vs 7100-ish, respectively).

Interesting!
The interesting thing wasn’t the power usage difference between them (well, I expected a drop in power usage and got it), but the difference in power usage when I used a 400 W PSU with the new setup compared to a 500 W PSU. For the record, the only thing I changed was the PSU. No settings changed, no other hardware changed. I didn’t even run windows updates in between them. Unfortunately, I don’t have the numbers for the D930 with the 500W PSU, because I already swapped it for the other motherboard when I thought about trying that.

The details
In the table below you can see power usage that I measured (it was oscillating a bit sometimes (a few percentage of the total), I took a number that looked average). The activities are: Busy (Battlefield: Bad Company 2, ingame), Idle (Windows desktop, no programs running), Windows Standby (as the name implies), Off (shutdown, cable plugged in).

Anyway, the measurements:

As expected, there is some difference between the Pentium D930 and the C2D T5500 (max 115 W, min 3 W), even forget that the D930 is terrible at being Standby (I mean: 121 W? really?) but look at the difference between the same C2D with a 400 W and 500 W PSU (max 25 W, min 2 W). I guess the 400 W PSU I have is more power efficient. By the way, I rechecked 3DMark2006 for both the 400 W and 500 W PSU, both are around 7100-ish, so no big change there.

Update: 400 W PSU is FSP Group Inc, 500 W PSU is Coolermaster

After seeing a similar construction at a friend’s place (hello Pieter!), I decided to build a key board. Ingredients: a couple of hard disks (broken or very old), a piece of wooden board some screws. In the image on the right, you see a couple of leftover magnets (there are one or two magnets per hard disk, so you can imagine how many hard disks I had). You see the magnets marked with ‘N’ for ‘North’ so I know which way to orient them.

I’ve screwed some magnets on the wooden board and placed caps over it (to protect the magnets and for aestetic reasons). The caps are actually parts of hard disks as well. Then I’ve put the key board on the wall and threw keys at it. I know it’s a bit cheesy, but technically, it is a board for keys :P You can see the result in the image below. I’ve noticed that not all keys are magnetic, but most key rings are, so most keys will still stick to the board.