Thanks, the 2nd link posted had an answer in its 2nd page.
Sorry, but you cannot specify individual files or file types to not preload. You cab only specify it to preload the program files, boot files, or the default of both.
I guess that means I'll just have to hope prefetch learns some more, and otherwise deal with it and be happy that it prefetches what it does, rather than being upset that it doesn't prefetch enough.
Thanks for the links!