"USB device not recognised" notification keeps repeatedly flashing up

What type of device is connected?

I had this problem. Turned out to be a faulty micro USB connector. I bought a new one and it stopped happening.

When you connect a USB device, the USB controller on m/b senses an electrical change on the bus so it knows there's a device change. Then there's a h/w handshake between the m/b controller and remote device. When handshake done, the device sends Windows its Device Descriptor (identifying itself)

If the handshake fails or device can't send its descriptor, Windows knows something is out there but has no idea what it is (because it doesn't receive a Device Descriptor). Thus you get "Not Recognized" message. Disabling doesn't help as you can't really disable an Unknown device (Without a device descriptor, windows has no way to identify what to disable!)

Some USB device is connecting the bus but the handshake is failing or device can't send its descriptor. What USB device is connected but not in Device Manager/not working? Have you tried disconnecting the hub? connecting devices directly to computer usb?

I had this for a dumb device - it just had a battery that needed charging, nothing in it that could possibly be recognized or used by the PC. It started intermittently after about six months of use, got more regular and eventually stopped charging. A new usb cable fixed the problem, but only for another six months. Turns out the micro usb socket on the device was poor quality and gradually destroyed any connector that was plugged into it. some of the connections shorting together was what fooled the PC into thinking there was an active device on the end of the cable.

What's your device? If it's connected by a cable, try a new cable.

Generally speaking, USB has a single cable limit of 16 Feet unless using an Active cable [expensive] for longer runs. USB may be extendable using Self-powered hubs, i.e. Computer with cable to a Hub with another cable from Hub to a Device.

ComputerGeek said:

When you connect a USB device, the USB controller on m/b senses an electrical change on the bus so it knows there's a device change. Then there's a h/w handshake between the m/b controller and remote device. When handshake done, the device sends Windows its Device Descriptor (identifying itself)

If the handshake fails or device can't send its descriptor, Windows knows something is out there but has no idea what it is (because it doesn't receive a Device Descriptor). Thus you get "Not Recognized" message. Disabling doesn't help as you can't really disable an Unknown device (Without a device descriptor, windows has no way to identify what to disable!)
Some USB device is connecting the bus but the handshake is failing or device can't send its descriptor. What USB device is connected but not in Device Manager/not working? Have you tried disconnecting the hub? connecting devices directly to computer usb?

All I've done is to disconnect all usb devices physically and then reconnect (without a reboot). But to no avail. I don't want to have to uninstall all my usb drivers as this seems like taking a hammer to open a can of beans!!

Though I've disabled the notifications all this does is visually disable the notifications I can still hear the notification alert!!

Bree said:

I had this for a dumb device - it just had a battery that needed charging, nothing in it that could possibly be recognized or used by the PC. It started intermittently after about six months of use, got more regular and eventually stopped charging. A new usb cable fixed the problem, but only for another six months. Turns out the micro usb socket on the device was poor quality and gradually destroyed any connector that was plugged into it. some of the connections shorting together was what fooled the PC into thinking there was an active device on the end of the cable.

What's your device? If it's connected by a cable, try a new cable.

No idea. This has been happening since connecting something but I can't remember what it was now. But your theory of an electrical short on the USB connections is a good one so I will test this out.

WDG said:

I had this problem. Turned out to be a faulty micro USB connector. I bought a new one and it stopped happening.

Yes this might very well be the issue indeed. I've got a very short USB cable attached which has something connected on the other end ad hoc that may very well be the culprit.