1 of 3 USB Ports Stopped Working Post Windows 8.1 Upgrade

Did you check the power options? USB Selective suspend could be the problem

Windows Key + X > Control Panel > Power Options > Change Plan Settings > Change Advanced Settings > USB settings > toggle the 'USB Selective suspend' setting to enabled if it is disabled, or disabled if it is enabled. Apply and reboot. If it doesn't work upon reboot, toggle it one more time and reboot again.

Thanks a lot for the suggestions, but no luck. Tried a few toggles and reboots. No change.

Does the port show up in Device manager? If so, is it showing an error? What driver is it using? If powershare is a proprietary feature from Dell, I don't think the Microsoft system drivers will support its functionality.

Did you install the chipset and/or USB drivers from Dell?

Yeah I've installed every available driver. There is one device under "other devices" which does not have a driver, not available from MS. Maybe this is it. No errors, not sure which driver it is, as there are 3 USB ports and 7 drivers installed, plus the one under other devices which may be it. I've tried a resintall of W8.1 today and still not working. I'd say it's either a faulty motherboard or this missing device driver.

Thanks for the help

It's fixed itself. Just by chance I've been having a few issues trying to setup UEFI with Windows, so after about 3 installs, trying different and unrelated things, the USB port is working again. Amazing!