I have swapped the Motherboard in my PC and the case LEDs for the HDD activity and power switch are proprietary Dell 730x. The LEDs have separate +5v but share a ground. Power is supplied to both LEDs 5v constant, the on off switching is done on the ground side. With the shared ground both the HDD LED and power switch LED flash.

I need to create a circuit that with take the on off switching of the ground to switch the +5v on and off. This will be very light load only running 1 LED at 5v.

 

Can you separate the ground paths on the LEDs?

 

I need to create a circuit that with take the on off switching of the ground to switch the +5v on and off.

A high-side PNP driver should work for that (below):
The LED (yellow trace) turns on when the PNP base R2 resistor is grounded (green trace high).

Note that the emitter of the PNP goes to 5V and the collector is connected to the LED (the resistor Rsim, is just for the simulation).

 

You can use a MOSFET or relay to switch both +5V and ground for LED control, depending on your current requirements.

 

At least some hard drives have a two wire connection for an indicator LED. I suggest checking to see if yours has such a connection. Simpler and safer.