HOly $(#$&. Maybe you and your dad can make it into a project one day to clean up those cables. Pull all of them out and get some new CAT5e cable in there then tie it up in bundles neatly. That should be fun.
THe messiest cables in my house is of course, behind my computer desk. You don't want to look back there. I have power cables, USB cables, cable lines, etc all running back there. It looks similar to your dad's office but not as much cables.