My TV model is 26PFL5522D/05

I am trying to connect my laptop computer to my TV but unfortunately am having some trouble getting the sound to work through the TV. My laptop only has a VGA output. I know the instruction manual says that the TV does not support VGA input so I purchased a VGA to HDMI converter box to plug into the TV HDMI input.

Here is what I have tried so far:

1. I have the VGA cable going from the laptop plus the audio cable from the laptop's headphone jack going into the converter box. I then have an HDMI cable running from the converter box to the TV. The picture works perfectly but I do not have any sound. I made sure the mute button is off and turned the volume all the way up but still no success.

I did the same exact setup but instead fed the HDMI cable into a monitor that has its own integrated speakers which worked fine with both picture and sound. Because of this I know there's nothing wrong with the input, the converter box so I can only naturally assume it is to do with the TV?

2. Instead of feeding the audio input into the converter box, I then tried connecting the audio cable into R/L inputs of EXT3 like it suggests in the manual but again no success.

With what I did in (1) above, do I need to enable something on the TV so that it recognises the sound as well? I've tried both HDMI input sockets but they are the same - i.e. picture only.

I may be wrong but I don't see how (2) works, which is the suggested connection in the manual - i.e. connect the DVI output from the computer to HDMI 1 or HDMI 2 (admittedly my laptop is not DVI output but that is why I have the converter box) and then connect the R/L audio cables to EXT3. Then using the remote select the source as HDMI. Following this instruction and selecting HDMI as the source, how will the TV know that sound is coming from EXT3? For example, I have followed this and selecting HDMI will give me the picture (but no sound and hence my original predicament). Selecting EXT3 will give me sound but no picture!

I hope the above information is enough to go by but if any more information is required, I am happy to provide.

Here is a link to the instruction manual:

And here is an example of a converter box that I have:

I would be most grateful if anyone could provide some assistance and guidance on how I can get the sound working.

Many thanks