If you have structured the file system properly, all the documents that you wish to save.........those that have nothing to do with the programs.........are under the folder "My documents".

This entire folder needs to be duplicated on a CD-ROM or an external drive because it all will be lost when you reinstall the operating system.

You'll need to check the machine carefully to see if you have any files that are not under "my documents". Anything that you don't backup prior to the reinstall will be gone.