Nero Backitup Problem

I have some files someone sent me archived to dvd with Nero’s Backitup program. The file is 11 gigs and spread over 3 discs. I’m a mac person and fairly limited in windows experience, but I found a pc running windows xp and Nero 7. When I try to open the archive, it acts like it’s going to work, but it only copies a small amount off each disc before prompting me to insert the next disc. After it’s gone through all the discs, it tells me the file has been restored successfully but it’s usually only between 6-12 MB?

Has anybody ever experienced this?