Click. Click. Click. That isn't your mouse, that's the sound of Microsoft trying to make you go crazy. Lucky for you, there is a cure.
I started going insane when I started using iMacros, and I had a script running that would refresh a page every 20 seconds. Click. It was for a stupid game that makes it so you have no life by checking it every fifteen minutes. Click. I didn't want to have to deal with logging in so frequently. Click. If you must know what game it is, it's Knighthood from Facebook. Click. In fact I might as well toss in a pitch about becoming my vassal while I'm at it. Click here to join me. Anyway... No matter your Windows platform, you will need to go to your sound settings from the Control Panel. Go to heck you clicking noise!
Go to Start –> Control Panel –> Hardware and Sound.
Under Sound, click Change System Sounds.
Big list of programs? Good. Scroll down to see Windows Explorer. There choose Start Navigation and from the Sounds drop down menu choose None. Click OK.
Windows 95/98/2000
Go to Start -> Settings -> Control Panel.
Open "Sounds and Multimedia" control panel.
Choose Sounds. Scroll down to the "Sound Events" window until you reach "Windows Explorer" and under this you will find "Start Navigation."
Click on "Start Navigation" and you will see a .wav file appear in the "Name:" box. You're about to delete the most annoying thing since chicken pox.
In the "Name:" drop down menu, select (None) and then hit "OK." Congratulations, now sound will have meaning again.
Windows XP/NT/Server 2003
Open the Start Menu -> Settings -> Control Panel.
Open "Sounds" control panel. In this control panel, Scroll down in the events window until you reach "Windows Explorer" and under this you will find "Start Navigation."
Click on "Start Navigation" and you will see a .wav file appear in the "Name:" box. You're about to delete the most annoying thing since poison ivy.
In the "Name:" drop down menu, select (None) and then hit "OK". This will set no sound to be played when you're navigating on the web.
Backtracking?
To re-enable just repeat the steps and instead of clicking none, pick something else. (There's a big list)
Virus warning
ushdfgakjasgh says re Disabling the clicking sound from Internet Explorer: "shouldn't disable that sound, actually, it's sometimes the first thing that tells you you have a virus."