How to stop beep sound from your windows...

Beep sound from your pc very annoying? I use my pc to access as/400 machine. My company's application (insurance system) always give me beep sound if i do not fill in the important field. Very annoying!!! I just want to test and understand the system. I don't know which field is the important field (because i'm a new staff). The beeping sound is so loud that all people in my office can hear it (it shows that i'm accessing the system, my bos know that i'm doing my work, training.. but it is so loud!!! beep.. beep...). I've turn off the sound from the Volume Control, but the beeping sound still there. Oooo, it's the server/machine AS/400 that give the order to my pc to initiate the beep sound (i think)... I must kill that sound... But how???

1) Open Command Prompt
2) Type net stop beep
3) Problem solve, hehehe