Paddy 6 Posting Whiz in Training

I'm not 100% sure what the problem is, so forgive me if this is the wrong place to post :)

I use Windows XP Pro, and I burnt a DVD-R with about 2 or 3 sessions. I used Nero to burn it, and Nero warned me that any session burnt after the first may be unreadable in some older systems, specifically older than XP. The person I was burning the DVD-R for uses XP, so I went ahead and burnt the disc as a multisession thinking that it would work fine on her system. She received the disc today, and the files I burnt after the first session are invisible to her system. Is there any way of retrieving the data from the disc without her having to send it back to me to be re-burnt in one session? As I said, the first session I burnt shows up fine.

Thanks for your time! :D