Thanks for all of the help. I deleted the files on the Mac and reinstalled them, with no change in outcome. I then put the USB with the files on them and tried to open them from that source. Many would then open, but with several caveats...formulas didn't transfer,was one. So, it looks like there is a compatibility issue, that short of purchasing a Mac Office or Excel program, that prevents Numbers from accessing the original files. Since I've made the decision to fully transfer to the Apple culture, I'll just rewrite the few files I may need in the Numbers format. Once again...thanks for all of the assists!