Crackling issue in my headphones

Hello,

and thank you for your responses, my problem is as follows:

(before I start, here's my setup: Windows 7 / Firefox 10.0.2)

I recently bought a Tritton ax 180 headset for 80 euros (not of bad quality according to a lot of users); this headset is compatible with Xbox, PS3, and PC thanks to a system that allows switching between two mic configurations: pc1-ps3 / pc2-Xbox

When I put my headset on pc1-ps3 and call on Skype, I hear a continuous hiss in my headset that stops only when I disable the microphone in my Windows settings (or when I completely lower the sound of my headset), which isn’t very useful since I can’t hear anyone anymore...
This hiss, which isn’t very loud, quickly gives me a terrible headache :s
I specify that despite this hiss, I can hear my correspondents and they hear me very well too.
- When I'm not doing anything, there is no hiss
- It also triggers when I go to the "Recording" tab in my audio settings
- It also triggers when I go to the "Tools" tab in Skype without calling

(it seems that the hiss triggers when the microphone is "called" by the software or the PC)
(it's not feedback)

When I put my headset on pc2_xbox, there I have another problem: the microphone emits crackling depending on what I do, let me explain:

When I move my mouse, I hear a faint crackling, when I hover over desktop icons and they highlight, I hear crackles, when I type on the keyboard, I hear a crackle for each key pressed, when I go online and an ad flashes, the crackles flash too...
And let’s not talk about games! When I play, my friends think I’m in a helicopter!
I only hear these crackles when I enable voice feedback.

I’ve tried a lot of things: plugging my PC into a dedicated outlet, moving my microphone away from anything that could cause interference, unplugging everything unnecessary
Updating all my drivers, I plugged my headset into the front and back...
I’ve been on numerous forums (I’ve searched more web than Spider-Man himself! But nothing works, I haven’t found a solution)

I ended up thinking that the problem came from the PC, and I tried to plug the microphone into the line-in jack of the PC, but the microphone sound is not strong enough, and there are still crackles.

I’m out of solutions please can you help me?

Thank you
Plug