Booting up laptop, when i start my laptop it gives an option of more that one vista?

Booting up laptop, when i start my laptop it gives an option of more that one vista?

Hi, recently i decided to reinstall Windows Vista using the disc that came with my computer, i followed the instructions step by step and finally had it installed again, however when i start my laptop up it gives me the option to go onto this new vista (holding new account) or old vista (holding old account), this is quite annoying i only wanted to make my laptop run quicker like when i first got it.
Does anyone please no how to remove one of these Vistas?