Short answer from that forum is that you can't do it unless you "play" the content from the PVR and live capture/record it on your PC, which is a terrible solution IMHO. It has an ethernet, but that only streams content, it doesn't allow you access to the source files. Having said that, if you can stream the media from the device, would that solve your problem? The device allows you to add an external e-sata drive to expand access, but apparently it encodes all the content with the chief purpose of stopping you plugging the drive into another device or computer and accessing the files. Seems like they've put effort in to making what you want to do very hard!
If you have a newer model than the one they're discussing in that forum, there may be other options.