https://answers.microsoft.com/en-us/windows/forum/windows_8-hardware/usb20-driver-webcam-not-recognized-when-upgrading/90924e44-97c7-4b19-89e6-3a1e381a0302

I posted the following on Sony's customer support community.  This is the best solution at the moment.  My video camera has worked consistently for the last week:

The webcam relies on Microsoft's ksthunk.sys and usbvideo.sys drivers to work.  I had installed the fresh USB2.0 Camera entry early yesterday but the ArcSoft webcam software [apparently] was somehow blocking it.  I remember removing the ArcSoft software yesterday afternoon and didn't observe any change to the device's status, but today it showed up as if nothing had ever happened.

So, to get your webcam back in order, first make sure ArcSoft webcam software has been removed from your laptop, just to be safe. Sony also published a Windows 8 64-bit removal routine that presumably takes care of the offending portion, but I haven't tested this out. 

Now, you'll need to install the >>> Microsoft <<< device driver(s) as follows:

1.  In Windows 8, got to the bottom left corner, right-click on the mini Start screen, and select Device Manager.

2.  In the top menu, click on View and select "Show hidden devices".

3.  Go to the Imaging [D]evices section and right-click on the grayed-out USB2.0 video entry (or the grayed-out entry that correponds to your internal webcam) and select "Update Driver Software".

4.  Select "Browse my computer for driver software".  Counterintuitive, but it's the right choice.

5.  Select "Let me pick from a list of device drivers on my computer".

6.  Select Microsoft and USB Video Device.
