[Nexus 7 Q&A, Help & Troubleshooting] Favog:
I have an Asus Nexus 7 tablet that over a year ago I rooted and flashed and maybe a few other things, I don't fully remember, but I did get it to run the Nitrogen OS successfully, and since then I've used it with no problems. But the other day I plugged it into my PC via USB cable as I always do when I want to load a movie or whatever, and this time my PC refused to have anything to do with it. Immediately upon plugging it into my desktop's USB 3.0 (2.0 port does the same thing) I get this Windows 10 notification: "USB Device Not Recognized. The last USB device you connected to this computer has malfunctioned and Windows does not recognize it." When I check under Device Manager I see a yellow triangle warning under Universal Serial Bus controllers that says, "Unknown USB Device (Device Descriptor Request Failed)." And that's as far as I can go. There is no mention of ASUS, Nexus, or Android anywhere else in Device Manager. I've checked under all the headings.

It seems Windows 10 knows something has been connected when I plug in via USB but it doesn't know what to do with the device. I've searched the Internet high and low for a solution but nothing works. Here's what I've tried:

1) Uninstalled the yellow triangle error driver from Device Manager, checked for new hardware, got the yellow triangle back.

2) Tried updating driver but "You have the latest driver installed."

3) Tried installing USB driver from Google and "the operation completed successfully" but the problem remains even after reboot.

4) Went to Developer Options and ensured USB debugging is turned on and MTP is selected in USB Configuration. When I turn USB Debugging on and off with the Nexus connected via USB, Windows 10 reacts, but only to tell me with each change that I have an "unknown USB device attached," basically all the original error messages. I get the same errors whether I'm set for MTP or Camera or charge only or any of the other options.

5) Learned others have found a bad cable can cause my problem so I located three spare cables around the house and none worked. So I ordered a fresh new data cable from Amazon which arrived today -- but the problem remains.

6) I have a triple-boot PC. All three OS installations are Win10 but installed separately on different drives -- one of them is from the Microsoft Insider program, so should be the latest and greatest -- but I have the exact same problem on all three.

7) Wondered if maybe Linux would work so tried Knoppix live boot disk and even did a full installation of Zorin on a separate HDD. Neither version of Linux recognized that any Android device was attached. I even ran a "find-mtp" Linux program but it saw nothing.

8) Installed Wondershare Mobile Go and Syncios Data Transfer -- both are programs for dealing with Android devices via USB on a PC -- and neither sees my Nexus. And I guess there's no way they could as the Nexus doesn't appear in Device Manager.

8) Reset the Nexus to factory settings. All my apps and so forth are gone but the problem remains exactly the same.

I've been at this for about a week now so there are probably other things I've tried and forgotten about but nothing has worked. If I had another Android device I'd see if the computer recognizes it via USB but I don't have one. Maybe I can get a friend to help me out. I'm grasping at straws.

One more thing -- I don't remember whether I've ever before communicated with this Nexus on my current computer. In May of this year my old Asus MBO failed and I've built a new computer around an Asus Prime X299-A. It's working great, its USB ports are giving me no problems with anything else I throw at them, but I'm wondering of maybe I've got something set wrong in BIOS (UEFI). I've gone through every USB setting I can find in BIOS and no changes offered seem appropriate. But I've tried them this way and that with no apparent effect. And as I said, USB 3.0 and 2.0 are working great for everything else.

And when I wrote that last paragraph it hit me that I should try the spare PC I keep in a closet. Duh. So,

9) Tried a different PC, a spare Win10 system I built from spare parts from my old system plus an el cheapo MBO. This is a TOTALLY DIFFERENT COMPUTER -- but the problem is exactly the same.

It can't be the Nitrogen OS -- I just can't go there. It's been working perfectly for over a year, no glitches whatsoever. How could it suddenly decide to stop connecting via USB? I've pulled all my hair -- totally bald now, but that didn't work either. Any other ideas? Anybody? Toss the Nexus in the trash? That would be no fun. And it does work, though with the factory reset I've erased all the kids movies I was keeping on it for the young ones who occasionally visit and I have no way to put them back. I dunno what to try next ....