W2k NT Backup tape shows as unrecognised

I’ve got a DDS4 tape that is showing as Unrecognised by NT Backup on a Windows 2000 server SP4. However, this tape was made interactively a week ago and fully verified as ok – I have the log printed off to prove it. Is there any way to recover data from these sort of problems? I know NT Backup is c**p but it’s all I have. Is there any recovery software I can download? The company here won’t spend any cash so I need something quick and cheap (free?) to get the data off this tape.

Many thanks