OS 10.4 - mini crash - flickering screen

I downloaded a torrent version of Stuffit expander and now I get a problem when in a Finder window the screen flickers and then loses its icons for a second. I am usually left one step back from where I started before it happened. I know! I shouldn't download unverified software from unverified places. I am that div but could do with some help to put it right. I have tried deleting any relevant files but this has not fixed it.