When renaming a dc5 file, and there is a reference file used the program seems to lock up, and at this time creates unlimited drawings on your hard drive under the Datacad directory untill your hard drive is full. I have found that this is caused because the dc5 file has a layer locked and the drawing can not be renamed. FYI
When you are renaming the file, are you just right-clicking on it in the Windows Explorer? If so, it would likely work a lot better if you opened it in DataCAD and do a Save As instead.