How do I open a WP Entrust signed doent? ?

Two years ago, I backed up no less than 25 doents on a CD. I recently found the CD and wanted to put the doents on my computer, however, I've made a switch from Windows computers to a Mac. When I tried to pull up the files on my Mac, since I didn't have Microsoft Word, the original program that the files were written on, they wouldn't open. I put the CD in a friend's computer, and she runs off Vista, and while one file with pictures came up, when I opened the file for the doents, it wouldn't show any of the 25 files I had saved. Another friend still runs off Windows XP, and I loaded the CD up. Now the files will show, but when I try to open them, the computer tells me that they are "read only files" and that I may modify them, but only if I save it under a new name. I click yes, and another box pops up, asking me to "convert file format from", and while I've chosen the format that I know the file was created in, it tells me it's an unknown file format. Help?