Lost PC to TV sound

I have my PC set up using a TV as a monitor. Until recently sound form the PC also played over the TV speakers.

In a moment of stupidity, while I was trying to connect to my external amp, via the headphone socket, I had the 'Speakers Properties' open, and I accidentally disabled the TV speakers. After that, the taskbar speaker icon had a cross on it, stating the speakers weren't connected.

Fast forward to this evening, I've restarted the PC after installing this month's updates, and the cross against the speaker icon is gone. According to Windows everything is working okay, but I still have no sound to the TV. Looking at the sound properties again, the tv/speakers is not listed.

The headphone socket, when I try it has been working normally throughout.

I've tried removing & reconnecting the cable, but it hasn't helped.
I've plugged a usb stick into the TV to test the speakers, and they are still working okay, so I'm sure it's just because of my stupid selection of the 'Don't use this device (disable)' option that is causing the issue.
I've also tried Windows - Add new Hardware, but it hasn't picked up anything.

I've been unable to find an answer via Google, so hoping someone here can advise. I don't really want to go out and buy some external speakers when the TV ones are good enough.

A few hopefully useful details, though I'll no doubt miss something.

The pc itself is a Zoostorm Desktop PC Intel Core i5-4460 8GB DDR3 Ram 2TB HDD from ebuyer, with Windows 7 installed.
The TV (32" LG) is connected using the PC's DVI socket to TV HDMI. (I have a second monitor using the VGA socket)

Any suggestions on restoring the sound from the tv speakers would be appreciated.