sorry for not replying sooner. you cannot delete the administrator account. it should not be showing when you first start your computer up. if it is, that means you should be able to disable it by using another account with admin access. the administrator account is a hidden backdoor basically.
as for your dvd drive being slow, can you describe this slowness to me? if you mean dvd movies are playing slower than normal speed or is skipping than you either have a scratched disc or your computer is not keeping up with the data transfer.
if so you should rip the movies to your hard disk and play them off that instead. www.dvddecrytper.com
is a free ripping software that can accomplish this.