Check the A1200 led cable and you'll see that there are 3 together, then the "key" (missing pin), and then a lone whire. The A1200 use a common ground (the single pin) and the other 3 whires are for each led.
Now check the leds crom your tower and you'll see that they are of the same kind but only in pairs (2 pins). That's because they don't use a common ground so each led got it's own ground.
Now lets say you want to hook up HD to the HD led, the Power led to the power led and the floppy led to lets say turbo led. Then what you would need is just to get a 5 pin connector (such as the one sitting on the A1200 led whire). Then you connect the colored whire from each of the leds to the tower to pin 1, 2 and 3 on the connector and then you connect all ground cables together and put them at pin 5.
I'll do a quick drawing for you... after i've posted this.
