Looks like you're using Snapshots - delete the snapshots from within Hyper-V Manager and those files should go away. You should not be using snapshots on a production server for very long. Sure, 1-2 weeks, but beyond that they should be deleted so that the
files can be merged.
Also, if this is not snapshots, it may be your backup methods crashed during backup and failed to remove these files. If that's the case, they would be fine to remove.
Adam Marshall, MCSE: Security
http://www.adamj.org