I have a DC server running from one year, but the last six months has not been managed at all. The result is that the pc, policy and other objects in DC are not in sync with the real equipment presents in the company. I.e. I have several pc not anymore in active directory but that are presents in DC inventory.  

How can I fix this situation ? Should I delete the whole DB , if so how ? The problem also affects the license as we're running out of space as many "dead" pc are still presents.

Also there is a way to maintain in sync DC with the active directory ? Or I should delete the objects pc in DC after I did remove it from company Domain ?

For the moment thanks!