This will show you how to clean up that cable mess below your desk . I have read multiple articles on this site about great ways to manage your cables. I believe this method is extremely flexible for various cable paths and extremely cheap!
1) Large (2 inch) Binder Clips - under $4 for a box of 12
2) 3/4" Wood Screws - under $1 for a box
3) Washers - under $1 for a box
Unplug all the devices and separate the cables from each other.
Gather your supplies. I am using 3/4 inch length screws because my desk is 1 inch thick. It is important that you take the time to measure your desktop. Pick a screw length that is at least 1/4 inch shorter than the thickness of your desktop. A sure fire way to ruin your day is to finish the project and find that you now have 8 screws sticking up through your desktop.