If the beeps are all the same length it would be a video adapter problem. But, since you have a video display that does not seem likely. Is there a pattern (like 1 beep - a pause - 3 beeps - a pause - 4 beeps)?
You might try this sequence it might clear the CMOS memory.
1.) Easy way: Fn+11
- hold the Fn-key pressed,
- switch on power,
- continuously tap on F11
This will lead to the flashing LEDs, cycling on and off.
Letting loose F11, the machine will boot again and show the BIOS error-msg "162 system options not set". Use F1 to save the setting.
Caveat: All settings are set back to factory standard. You'll have to enter a correct date/time.