Illustrator "future" backward compatible with AI 10?

Hi - I am a complete newbie. I use AI about twice a year when we are putting some figure together for academic type papers.

My hard drive crashed. The new hard drive needed AI installing. We actually had disks for AI 10. I installed AI 10 on the new hard drive assuming this was the version that had been on my old hard drive. When I tried to open my previously saved files, I got an error message saying the files were from a newer AI version (a possibility, we might have a got a free upgrade at some point) and that I needed to save my files using the older (AI 10) version. The files would not actually display the image but the file tab/artboard had the original name of my file on it so I selected save from the drop down menu, gave the file a different name and hit save. When I tried to open the file with AI 10, the file still would not open. Any ideas? The files were eps files if it helps. 

We can sign up for the creative cloud package through the university IT dept.. Any advice from the community about whether these older files would open using the up to date AI?

Thank you very much for any help you provide!!