A Plug and Play operation may also not correctly recognize a USB device for the following reasons:
- An external power failure occurs on the powered hub or on the device.
- A device is unplugged while writing files.
- A device driver is out of date, corrupted, or incompatible.
- A virus
Try the usb in another computer. if the problem is still there then the usb might be the problem.If it works on another computer then it is a problem with either your usb port or power management. You can install a new usb port driver. You can do this through device manager by right clicking on the usb device after expanding and right click to update driver. To change the power management: 1. Click Start, click Run, type Devmgmt.msc, and then click OK. The Device Manager window opens.2. Expand Universal Serial Bus controllers.3. Right-click a USB Root Hub in the list, and then click Properties. The USB Root Hub Properties dialog box is displayed.4. Click the Power Management tab.5. Click to clear the Allow the computer to turn off this device to save power check box, and then click OK.6. Repeat steps 3 through 6 for each USB Root Hub in the list.7. On the Action menu, click Scan for hardware changes. 8. It should recognise the usb.Note: When you are in this window look around on other tabs. There is an option to reset usb hubs too. You can try that. Note: Go to disk management to see if the usb shows up there. See if it has a label. How to open disk management:1. Go to the start menu.2. Right click on my computer or computer.3. Choose manage from the menu.4. Then click on