Computer making strange sound effects

[The Claw]

Lately my computer has been randomly making sounds. When I am off the computer and all of my programs are closes, I will hear a one second clip from some sort of song. Other times my computer will make strange sound effects like a clump of sirt hitting a brick wall. Is this some sort of prankster virus, and If so, how do i get rid of it?

My Computer:
OS: WIndows XP Home
PC: Powerspec
Processor: Pentium D
Spyware Virus Protectors: Norton 360 and Spybot Search & Destroy
Year COmputer was Purchased: 2006

[Broni]

Are you the only user?

[The Claw]

No, I'm the only one.

[CBMatt]

Do you encounter these sounds in Safe Mode?
Do you encounter them primarily online, offline, or both?
Out of curiosity, do you have AOL, AIM, or any other instant messaging services?
Through your Control Panel, open up Sounds and Audio Devices.  Click on the Sounds tab.  Is your sound scheme set to Windows Default?

In order to eliminate the possibility of an infection, please read through this thread and post the requested logs...
http://www.computerhope.com/forum/index.php/topic,46313.0.html