Scratches and clicks when web browser updating. Why??

Firstly I'm not sure whether this is a hardware or software issue, so if you think I've posted this in the wrong place, feel free to let me know, or (if you're a mod) to move it.

For a while now when I'm using a web browser, I keep getting bursts of quiet noises through the headphones that I usually use.

With my usual browser (IE9) it's quiet scratches and soft clicks. (For those of you old enough to remember, they're like the clicks you used to get on the old telephones with a rotary dial as the dial returned to its starting point after each digit dialled).

I also get the scratchy noises if I use Chrome, so I doubt that it's just IE9 being crap.

I haven't a clue if this is normal (and if so, how can I stop the sounds being heard?) or abnormal. If it's abnormal, is it a sign that my PC needs fixing, and if so, what component? I am a heavy user of my PC and play a lot of games on it, so the poor machine does work hard!

I've run Belarc Advisor and there's a screenshot below. If you need any further info, please advise me. I'm using Windows Vista 64-bit, and would prefer not to have to upgrade the OS.

Incidentally, I'm computer literate but not a full-blown geek - I'd greatly appreciate any advice not using too much jargon or geek-talk!

Thank you in advance for reading, and I look forward to your suggestions or advice.