Aqua-Soft ForumsI'm serious.
This idea might be worth million$, when used right, but I give it away for free here.
Today I came to my office and turned on the notebook. WinXP booted and offered to input the password. I just touched the keyboard, when starnge sound filled all my office room. It was like the loudest whistle you could ever hear. It was so loud that my accountant hardly could cry to me through it. It was so loud, that my friend ran from the near office to see what's going on. Our manager came and asked, who turned on this alarm.
I thought that my notebook produces that sound. But there's nothing rotating so fast in it to make this whistling cry. I closed the notebook screen - nothing helped, it still whistled. I closed the speakers with my hand - no changes. I turned the notebook off - sound had gone.
So, that was my notebook. But what's wrong, why does it whistle so loud? What could whistle so loud in it? It is equipped with 0.5 watt stereo speakers. Is that their summary 1 watt power that deafed us? Seems like.
I turned on the notebook with headphones plugged in (this automatically disables speaker). Everything went fine, I could login without any alarms. Then I put a headphone sink nearby the internal microfone. Haedphones started to cry so loud that I could hear it from outside the office (but not so loud as it was before). Self-excitation! That's what it was!
Yesterday night I practiced in playing bass guitar. It was late night, so I plugged the guitar to the microfone plug of my notebook (there's no line input in it), turned it on and tuned for maximal loudness in Windows Sound Mixer. Of course, the headphones was pluuged in (with these little speaker I cannot hear any sound at frequencies below 250 Hz, it is useless for bass guitars). After that I played with please and then just turned the notebook off (i was too tired to set it all back). I just forgot what it leads to, when you have a microhpone amplified and connected to speakers - nearby the speakers.
So, the secret of magic discouraging anti-theft alarm in your notebook at absolutely no cost is to:
1) have your headphones plugged in
2) have your general sound volume and wave out volume at max;
3) have your microphone turned on for the playing (run sndvol32.exe, go to settings, find microphone there and put the check mark on it; press ok and in the main window put off the "Off" check mark under microfone unit)
4) drive your microphone high - tune it's volume to highest position and configure extra settings for microfone - most AC97 powered sound cards have 20db Boost option for microphone, other ones should have it too.
5) have nothing plugged in to your microphone plug
6) turn off the notebook
7) plug off the headphones 
Now the alarm is set. There might be 8) leave your notebook at some bench, hide and watch
Of course, when you turn on the PC, you should plug the headphones in first. If you don't like the ambience sound, just turn off the microfone in Windows Mixer (sndvol32.exe).
And remember of system requirements:
1) sound card
2) internal speakers (the more power the better )
3) internal microphone
