Whenever i use kazaa (or even have the programme open) my whole pc just slows down

No matter what other programme i use (whilst kazaa is open) it takes fookin ages to open up or do anything else on my pc, it even slows down my msn etc

As soon as i close the programme (kazaa) everything speeds back up again

Is there anything i can do to sort it out?
Any help will be apreciated

Thanks.