Okay ziad, first lets confirm the equipment, from what you posted, I went to the Orange Ibot web site. The only "Pro" webcam listed is the FireWire one with the headset. Is this what you are using?
If so, then I don't know if the headset plugs into the web-cam which then plugs into the FireWire port or if the headset plugs separately into the mic and headphone ports. If its the first, going in through the webcam, I can't help you, best I can suggest is to talk to Orange's tech support. However, if the headset plugs into the usual mic and headphones ports, then maybe. This is a well discussed problem area on the 88xx SAGERs.
I have a headset plugged in this way, via the mic/spdif port but not using the splitter cablek, just plugged directly in. The phones are plugged into the headphones port. It works really well, indeed, I have to modulate the volume to keep from hurting my ears. But it did take a bit to get the settings right.
First of all, you need to open the volumn dialog. Click on the volume icon in the tray or go to Sounds & Audio in the Control Panel, actual the latter is probably better as it will open up a lot more items you may need later anyway. In the volume dialog click on Options, then Properties, then Playback, where you should activate whatever items you want to use, this will put them up on the diaglog box so you can fiddle with them. Then click OK and go through the volume settings for each item on the volume dialog box. Make sure you have them on and not muted and at whatever volume level works. especially the Mic ones. Go to Microphone and click on Advanced , then deselect "Mic 2 Select" and select "Mic Boost". Go back and do the Then go back to Options, Properties and select Record and do the same routine, making sure to activate all the appropriate items but especially the Mic.
This should fix the problems. Hopefully it will. If not at first, then try it again, and once more if necessary. I haven't had to reboot to make these changes but if it doesn't work you might try that. Can't tell you the times I've done something exactly by the book, didn't work, tried it again, again exactly by the book, didn't work, tried it again, completely and exactly the same way, and it works. Don't know why, but I suspect there is a random stress program in Windows that senses your need for stress and activates strange, inexplicable frustrating failures when you are most likely to go postal. Anyway, I digress. I find a good rebooting or two can often help. I think that's where the term came from, the early geeks realized that often their machines just needed a good swift kick or "boot" now and then.
After all this, if you still aren't getting somewhere, try the Sounds & Audio dialog in Control Panel, on the Voice tab you can click on Test Hardware .... which will bring up a Test Wizard that will first show if your Mic is working and then if your speakers are working.
You might want to try the above with out your head set first just to see if you can get the system to work. Once its working, then try it with your Ibot headset.
Hope this helps. Good Luck.