Problems with video chatting/conferencing on ...

I dont knw whats the problem with my acer apire 5920.
I have tried installing windows xp, windows vista home premium and windows vista ultimate but i get the same problem everytime that video chatting wont work fine, it will be gud for few min and after that my computer always slows down and at 1 point i always have to end the video chat and restart my computer to make it work fine again. I have tried skype, google video and oovoo same prob with all the softwares.
I have no idea what the problem seems to be but basically i just use my laptop for video chatting only.