hp laserjet 2500 print again at flashing toner light / empty toner

hi all,

does anyone know how to print again if the printer says by the
flashing light the toner or the drum kit is empty? I can't believe
that the toner cartridge or the drum kit doesn't work again for a
while! The print quality is very good when the light starts to flash.
There are absolute no quality loss up to this moment.
the toner and the drum kit are to expensive to dump it before the
print
quality is poor.

thanks in advance
christian