For tape? Windows comes with MSBackup built-in, it works OK.
By OK I mean I saw countless commercial enterprises using it as their sole backup software for years.
It backs up. It tests the backup. It restores. Can do incremental backups too.
For DVD-R? any DVD burning app would do but I have a preference for Nero; it does have a HD backup function that will span multiple DVD-Rs when needed but I never tried it, I always use the "select files and burn one disc at a time" method.
The problem with tape drives is that they are usually slow unless you buy the latest and greatest (quite expensive) and they are SCSI, so you need a SCSI card.
The advantage is that the tape capacities are large so you can start the backup and go home, it will be done and verified the next day.
One example can be found here:
http://www.digitape.com/mm5/merchant.mvc?Screen=PROD&Sto re_Code=D&Product_Code=AITi1040s&Category_Code=AIT5
400 Gigabytes in one tape, tapes are $50 each.
