WD external hdd will not start up on a desktop pc but works on others

I have a WD Scorpio 25" hdd which is in a case case with a USB connecter interface used for extra storage.
It works with no problems with two W10 laptops when connected to them via USB cable. It immediately starts up spinning/humming.


My problem is when I try connecting it to my W7 desktop, its led light goes on but it struggles to start, jrepeatedly making the sound of trying to start up and stopping. I then tried plugging it into another USB port on the desktop with the same results.


The desktop works well with other 2.5" drives connected externally so I cant figure out why the external hd works normally on the laptops but cant manage to start on the desktop.
The drive has been tested with WD's lifeguard diagnostic tool and it tested normal. Any guesses as to what may be causing this problem??

USB 3 issues under Win7 ?

USB Port not providing enough power on Desktop? especially if other power using USB devices are on the same hub. Device manager should show power tab for different hubs , most are 500 milliamp I think.

Thanks for your suggestion, but when I attach a diifferent 2.5" external hdd via the desktop's usb ports it powers up with no problem.

I use 2 different types of 2.5" HDDs in cases, 1 type is the WDC My Passport which uses a single USB cable [1 is USB 2.0 and the other is USB 3.0 but backward compatible] and the other type is a empty case I put my own drives in. The 2nd type REQUIRES a Y-cable which 1 leg provides data and power and the 2nd leg is for additional power which is required based upon the power draw of the HDD plus the interface board with light. As mentioned, the power requirement of the HDD is important, I have a Toshiba 750GB in front of me that requires 5Volts at 1.0Amps, won't get enough from a single USB port. One might get a Self-Powered USB Hub which should help.