Help! annoying click sound

[highrise]

hi guys
I posted this on the German site, but have just found this English one - I hope someone can help. I have installed XAMPP on three separate machines and in every case, once it is installed I am troubled by a clicking sound. It sounds a lot like the sounds made when clicking a button, and is in two parts - a louder click, followed shortly after by a quieter one. It is INCREDIBLY annoying. I have done all kinds of virus / trojan checks and there is nothing coming up. I fairly confident that I have re-downloaded XAMPP from a safe place and it still does this. It also does it on both XP and Vista. There are only two things I know for sure:

- it definitely starts when I install XAMPP
- it can temporarily be stopped if I use CTRL-ALT-DELETE, shut down explorer.exe, and then restart that process. But it comes back later.

Does anyone have any ideas? it is driving me absolutely crazy as it happens every minute or so.