Dell XPS M1530 Beep Sound

I am using Dell xps m1530 from last 11 years... it came with pre installed windows vista..but recently i had formatted it and installed linux ubuntu 20 it works smooth and fine. Only issue is at time of startup or boot it creates continuous beep sound and  as soon enter button is pressed its gone. Can anyone help what is wrong with my machine ? And how to disable that sound?