either your memory [ram] or motherboard are knackered..
as youve said that you upgraded your ram this is what you need to do...
turn off your system - take 1 piece of teh ram out and boot.
if theres no beep thats the faulty ram.
keep doing this untill you find the responsible piece.
but remember to replace the working ram.
if its still doing it with the new ram try your old ram instead.
It could be a lot of things, unfortunately. How old is your computer? Also, have you changed any parts recently, or is your computer having any other symptoms aside from the sound at startup?
My system is quite old now as it is around 6 years now. I have upgraded my RAM very recently
what exactly is the sound...
2 fast beeps - 1 short beep
No, it is continuous beep sound and no interval inbetween