Hi, I have a secBo DVR as well and no problem with backup using DX client software, when I connect the DVR to the PC via the USB, the computer detects the DVR and you can then use the DXclient to backup the whole HDD to your PC, then it creates a file which is not readable yet, you need to choose the format (MPEG4, AVI etc..) to export the footage.
Can your PC detects the DVR at the first place when you connect the DVR to it? maybe there is a problem with the USB cable??