Hi Nigel,
Thank you so much for sharing the troubleshooting report details with us.
We have come across some instances on other forums where the users were able to resolve similar issues by uninstalling the existing sound card drivers from the computer and then reinstalling the latest Windows 8.1 compatible drivers from the computer manufacturer’s website. So, let us try uninstalling and reinstalling the audio drivers on the computer and check if that is helpful.
Uninstall and Reinstall the Audio Drivers
Step 1: Uninstall the Device Drivers
a) Press “Windows Logo” + “X” keys on the keyboard.
b) Click on “Device Manager” from that list.
c) Search for the Sound Card device from the device list, right click on it and then select “Uninstall”. On the un-installation window, if you have an option: “Delete the driver software for this device” you may select that and then remove the corrupted drivers from the computer.
d) Follow the on-screen instructions to complete it and the restart the computer if prompted.
After the restart, please open the Device Manager again and then click on the “Scan for hardware changes” button. Check if Windows 8.1 detects the Sound Card device and installs an appropriate driver automatically. If the issue still persists, then try the next step.
Step 2: Check Windows Updates for the latest drivers.
Check in Windows updates if any driver updates are available. If so, install the same and check if it helps.
a) Press “Windows Logo” + “W” keys from the keyboard.
b) Type “Updates” in the search bar and click on the icon “Windows Update” from the search result.
c) On the “Windows Update” window, click on the link: “Check for updates” from the left hand side of the window to receive a fresh list of updates.
d) If the updates are available, then install all the updates listed there.
If Windows Update does not offer the latest Windows 8.1 driver, then try the next step.
Step 3: Update Driver Software from the Manufacturer’s website:
Visit the Toshiba website, search for the latest Windows 8.1 compatible drivers for the sound card device and then download and install it on the computer. If you are unable to find an appropriate Windows 8.1 compatible driver for the computer model, then you may get the help from the Toshiba Support from this link:
Hope this resolves the issue. Please get back to us with the troubleshooting result.