|Remove a/c adapter input - and the battery.|
Remove both RAM sticks - carefully.
Clean the edge connectors with a soft pencil type erase; or if none available - a little isopropyl alchohol.
Re-insert one stick; then remove and re-inset again. Then do the same with the other stick - re-insert/remove, re-insert..
The remove/re-insert routine is to clean the sockets too...
Then reduce again to one stick and power up. If no beeps (hopefully there will be none) - power down and again remove the battery too.
Re-install the second stick.
Power up and see if "still no beep" and things now work OK?
Often RAM edge contacts can oxidise slightly over time; sometimes a stick can become slightly displaced... Either can produce error messages/codes on boot up. The above routine addresses both of those possibilities.