When discs are spinning in the drive it creates a lot of wobble, if the unit is stood up it makes a fair bit of low frequency noise because of this, if it's laid down it's not so bad but it's still vibrating, worried it may get worse or may cause problems with other parts of the 360, anyone else had this kind of problem?
the only way i got rid of it was to install to hard disk, still louder than my PS3 but tolerable 