DCP-o-matic is made by one developer in his spare time. As a project, we do not have any quality assurance department, testing team or anything like that. Though we try our best to ensure quality using automated testing, and by the great efforts of our users to find and report problems, bugs do get into the code and things do go wrong.
Though very undesirable, bugs in most parts of DCP-o-matic are usually not disastrous; they most often result in an error message, or some problem with a DCP. The Disk Writer tool, however, is a bit different. It obtains permission from your operating system to write directly to disks connected to the computer. Though we have done as much as we can to prevent problems, there is a chance that a bug in the Disk Writer could cause irretrievable data loss (for example, if the writer wrote to the wrong drive by mistake).
No such problems have been reported, nor found by us during testing, but I would like to warn you that they are possible. As always, make sure that you have backups (somewhere that is not directly connected to your computer) of anything that you do not want to lose.