I have an external HDD that's connected via USB and it's no longer detected on my PC and it was previously. It connects and is recognized right away on my wife's PC. I tried a different external HDD via USB connection and it's not recognized on my machine either, but is on hers.  Edit: they both show in Device Manager Win 8.1 when connected but not under Win devices and drives nor in Disk Management.

It doesn't matter which USB drive, 3.0, 2.0, front panel or MB in back.

Now here's the weird thing; any USB thumb drive I connect is instantly recognized and I have full access.

I uninstalled and reinstalled the USB Drivers and no change. I've searched for viruses, trojans, etc. and have negative results, thankfully. SSD health is 100%, temp running at 31C.

So, any suggestions?
 
System Specs:
 
MB-Asus Maximus Hero VII Z97
CPU: I-7 4790K stock settings
RAM-G.Skill sniper 16gb ddr3 2400mhz
SSD: Samsung 840 Pro 256GB
GPU: EVGA 980 SC with EK water block
Sound: Asus Essence STX
External HDDs tried-WD passport 500GB and Toshiba 3.0 1tB.
The system is water cooled, idle temps 26C for GPU and 28C for CPU. Load temps 37C GPU, 42C CPU. Ambient temp 26C.
If you need any other system specs I forgot let me know.

rlb9682
So here's your weirdness for the day. With the WD Passport evidently it was getting too much power via the USB cable so I went to Power Options in Device Manager and enabled selective power suspend. Voila! the drive shows up immediately and Win tells me it needs to initiate the drive.
 
 

Too much power??? Amps don't work that way. The drive only draws as much current as it needs. Volts are a different story, but all USB ports output a solid 5V, no more, no less.

With the drive not plugged into the USB port and the computer is powered on and the External HDD is powered on.....
Plug in the USB Cable and when you do this do you here the Windows Sound that tells you that you have inserted a USB Device?
 
I disable any Power Management on all the USB ports to all some of my older USB 1.0 and some 2.0 to work.
  
 
Click on Image for Larger View.

How about reinstalling the Universal Serial Bus controller drivers?

bcavnaugh

rlb9682
That's the problem though, the external HD gets power from the USB-not an external power source. http://www.amazon.com/Elements-Portable-Drive-Storage-WDBUZG5000ABK-NESN/dp/B00CI3BISU/ref=sr_1_1?ie=UTF8&qid=1433775720&sr=8-1&keywords=passport+500gb
 
When it's plugged in Windows does not detect the HD via USB unless I'm using the USB-Y cable now. http://www.amazon.com/eForCity-dual-Micro-B-Cable-Black/dp/B005M0ICG2/ref=sr_1_1?ie=UTF8&qid=1433775799&sr=8-1&keywords=USB+y-cable
 
Previously, I could plug this in the USB drive and Windows detected it, no problem.
 
And yeah, went back and disable the USB power management.

OK,
I do have that cable for my Blu-ray Player.
I have one new Charge Port that my WD will not work at all with one cable as well.
That is my Charging USB Port on my Laptop is what will not work with my WD.
It is like your USB Ports are not getting enough watts or aps to push the WD drive anymore.
I think that you 5VDC from your power supply may be the cause but who knows.
BTW I have been looking for an extra cable like the one in your link, Thanks.

Heh, I'm glad the link was useful for you.
And yeah, it seems like the USB ports aren't getting enough power any more. This started when I rebuilt my system. When I did that, I  changed PSU's from a Cooler Master V1000 to an EVGA 1000G2.
Even more strange to me is that EVGA sent me an email stating the 1000G2 was recalled( I can't remember if that was the wording) and they sent me a replacement so this is 2 different PSU's of the same model that, as far as I can tell, are not providing enough power to the USB ports.
 
But how do I diagnose this? Check the 5V with a PSU tester maybe but other than that?

bcavnaugh
Yep, I had my first 1300G2 recalled as well but are ok now.
I have 2 24-Pin MB Power Cables go bad from Corsair PSU and after that I switched over to EVGA PSU.
For the most part I use the 1300G2 an one 1600 G2 and two of the old 1500 Classified PSUs are working fine.
 
I wonder if you have a short on my motherboard stand offs?
Have you tested the WD drive in a different computer?
 
DROK® Digital Ampere Voltage Multimeter USB Meter, Dual-usb 2.0 HUB with 2 Ports for Fast Charging & Data Sync Charger Doctor Voltage Current Detector Meters Solar Panel Alignment Tester Mobile Power Panel Monitor Gauge Dc 3.2-10V 0-3A Red Blue LED Display
 

 
AboveTEK® USB Voltage Current Multimeter - USB

 
Yeah, I tested it on my wife's PC and it works fine, was detected right away with the original single USB cable. To check behind the MB I would have to a LOT of work removing the rigid tubing and everything else. Do you know of a way to test the 24 pin cable maybe besides a PSU tester?
 
Edit: I'll go ahead and order the USB multimeter and see what that tells me in the meantime.

No extra cable to swap out so I submitted a ticket with EVGA support. Hopefully they have some suggestions or a solution for me.