Reply #12: It's possible.

[iconoclastic cat]

Some people have created viruses that make computers act in very odd ways, including making PC's bark or insert text into documents before the document is printed.

My instincts tell me, however, that you may have changed some setting or installed something recently which is causing this sound to occur. I have two suggestions for you.
1. First, if you are running XP, check out the "events" that have occurred in the last hour.
To do this, go to Start>Control Panel>Administrative Tools>Event Viewer.
When the Event Viewer app is running, click on "Application" in the left frame. (This program is very similar to Windows Explorer, so you should be able to figure out what to do.)
Now, when you click "Application," you will see everything that every app has done since your last install, beginning with the most recent. Do any of the time stamps coincide with the sounds? If so, you should be able to tell which program is making the sounds and correct the issue by tweaking that program's settings.

If that doesn't work, try this:
2. Go to Start>Control Panel>Sounds and Audio Devices.
When the Sounds and Audio Devices window comes up, click on the "Sounds" tab on top. On this page, you will see a small window at the bottom that lists every sound and the event that triggers it. Look for that thunder sound and find out what event (or events) trigger it. If you can figure out why the sound is being triggered, you can stop it by tweaking whichever program is causing it. If it's a system error of some sort, you will have to go deeper into Windows to figure out how to stop it.