Audio/video sync issues

[Cinders]

Ok someone has to help me. I've just downloaded lods of films for my x-fi style and converted them to the right format (avi). The thing is that when they play there out of sinc big time, there's like five secs between vis and audio. The Creative central software I got a while a go with a mosic won't recognise my x-fi. It's driving me potty, can someone please help. Oh and I have a creative file converter and avi files are the only ones that work at all.