How about a new graphics card with a tv out and a video sender to plug into it and the reciever plugs into a connection on the back or side of the telly.
Depending on what motherboard you have depends on what card it has. Guessing a AGP as an older P4 machine.
Maybe this.
http://www.ebuyer.com/181290-pny-6200-512mb-with-vga...
http://www.ebay.co.uk/itm/Sound-and-Image-Wireless-A...
http://www.ebay.co.uk/itm/3-5mm-Jack-Male-Plug-2-RCA...
For sound card out.
2 links underneigth for reciever into TV. one or the other.
http://www.ebay.co.uk/itm/1-2m-Triple-RCA-Male-Cable...
http://www.ebay.co.uk/itm/1-M-RGB-Scart-3-RCA-Phono-...
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Soundcard video out to wireless sender.
http://www.ebay.co.uk/itm/1-2m-Single-Phono-Lead-RCA...
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http://www.ebay.co.uk/itm/3-5mm-3-5-jack-double-head...
To hang out the soundcard audio out so split audio out for wireless sender input and computer speakers.
just what I would do. Something like that.
Good old ebuyer and ebay but to be fair some of the leads end up in our poundland for £1 funny enough!.
Guessing the graphics card has a small yellow photo socket for TV out, mine did years ago but no picture on web site. Just an option, many cards to choose from.
Just picked one with the older AGP interface as guess you older computer would use.
Our thing from 1998, long gone was a rubbish PCI as AGP was nice and expensive and we did not have, guessed moved on again.
I think a tv out and leads to suit tv sender is needed. Some cards have HDMI out.
Shame computer was not in same roon and a nice 5m HDMI lead between back of computer hanging out of graphics card and into HDMI hole on back of telly, nice and neat, 1 cable, job done and digital all the way.
Can get nicer wireless transmitters but all depends on budget you have.
What I think anyway!.