I have never used this .xif format or ever heard of it, but I think you might want to try StarOffice and see if it can open this format. Also, does that xerox program support saving in other formats?
I think StarOffice might read that format. It is free and you can get if from Sun. It is a fairly large download though. Maybe you can burn a CD to let your students borrow to install, or buy one from Sun.