it has baffled me for a while now, the motherboard is a Gigabyte GA-MA770-UD3 (not exactly fantastic, but it does it's job) but i used to get it just after i built the multimedia PC and old parts from an old Packard Bell Multimedia PC packed up one by one i used to get this:
Power On
screech
beep (or beep sequence)
the location of the screeching is toward the front bottom of the case it's low pitched and lasts about a second in length, it's only recently it has started doing this on a clean startup, usually it was limited to errors.
even for me this is confusing.
the PC is about 8 months old now, i'll give specs upon request
if you can help, great