I think you will need to start the complete backup again.
6 DVDs? That seems rather a lot of data to backup. That's over 25 Gig compressed or about 50 Gig uncompressed. Have you tried clearing out any unwanted rubbish and emptying the recycle bin before doing a backup? Perhaps you need to partition your hard drive and organise your files to make your backup into several smaller backups, which will be easier to deal with.
Sorry if this doesn't seem much help, but a 50 Gig data backup seems a bit much at one go.