Using a workbench power supply:

You can use a regulated power supply to locate a shorted component.  Connect the negative output to the ground and positive to the fuse.  Slowly vary the output voltage and keep an eye on the current drawn. Soon as the current drawn about an amp or two, place your finger to any electronic components in the main board. Any component that gets very hot is the cause of the short circuit.

or

Use a current limiting power supply to power the +5V rail, and using a millivoltmeter, attach the + lead to the +5V rail and use the – lead to probe all the +5 V nodes of the board looking for the voltage increase as you get close to the short.