Is my ps2 okay?

i have a ps2 the new thin one and i bought this swap disc to play copeyed games, i opened the ps2 and i installed some chips in there and now when i turn on and off my ps2 a sound comes like a loud vibration for about 2 sec it sounds like it comes from the inside of the ps2 where the disc tray is but i can still play games normal without any problems. i just wanna know what that is.

John Mcbran
April 2005