go here which is the list of all microvitec files on aminet and do what the chap above said.
http://uk.aminet.net/aminetbin/find?microvitecreboot and you will have some other resoultions to try. I think i settled for one that was about 700*500. It has black borders down the left and right but is full hieght and has no flicker at all as it was about 60hz and a nice resolution to use
