Hi guys, here is the strangest problem I have ever experienced with my PC: Board: ASUSTeK COMPUTER INC. P9X79 PRO Rev 1.xx BIOS: American Megatrends Inc. ver. 4801 dated 07/25/2014 Running Windows 8.1 with all latest updates, even the optional ones. It has 2 ASMedia USB 3.0 controllers, one for the 2 ports on the front panel and one for 4 ports on the back. The driver I have installed for them is ASMedia ASM104x USB 3.0 host controller ver. 1.16.18.16034 dated 3/26/2014. I have 3 external USB 3.0 drives: - two of them are Seagate Expansion 4TB Desktop External Hard Drive USB 3.0 (STBV4000100), - one of them is Seagate Backup Plus 4TB Desktop External Hard Drive USB 3.0 (STCA4000100) Since last week my computer doesn't recognize the Backup Plus drive at all, but there is nothing wrong with the drive, because it works perfectly with my laptop, though strangely enough it's recognized by only two USB 3.0 ports of the laptop and not by the other to. As far as the Expansion drives are concerned the situation is even more weird, because one of them is recognized always, no matter to which USB port I plug it in (USB 3.0, or USB 2.0), even through the USB 3.0 hub. The other one, which is exactly the same model, but bought at a different time, so it probably has a different firmware, is recognized only if I connect it to one of the USB 3.0 ports on the front panel. Here is what I tried so far: 1. It's not related to USB 3.0 cable, or power supply of the external drives. 2. It's not related to the Power Options - all power saving options for all USB ports and controllers are turned off. 3. It doesn't seem to be related to IntelĀ® USB 3.0 eXtensible Host Controller Driver, which I installed for USB 3.0 support and then turned back to ASMedia drivers, which are a bit newer. 4. It's not related to Legacy USB support in BIOS, because I have it turned off now. So, I am running out of ideas. Can anybody help me? Your reply will be appreciated. Thanks! Peter