I'm not posting this on the Sennheiser forums because the headphones work flawlessly on our laptop.
However, in Windows 7, the headphones wouldn't work unless I plugged it into the Microphone jack (the pink one) and the microphone had to be plugged in to the Sound jack (the green one).
The headphones and microphone work fine and all, but Ventrilo won't work and I think it's because of this (I can't hear my m8s on Ventrilo no matter how much I try to change the settings)
I googled this and nothing came up so this must be Windows 7. My old headphones didn't have this problem. I also googled Sennheiser but to no avail.
p.s. how do I change my audio settings to Headphones? It's set to Speakers http://i49.tinypic.com/2mquwyp.png