Restore my laptop to factory settings

Hello,

I have a sony vaio laptop model number PCG-5B1M
It went abit awol at one point and i bought another one, i would like to know how to restore the laptop to its original factry settings so i can sell it on? I called SONY and they said i needed a recovery disk which would cost £35.Also when i stat the laptop and it asks me to choose O/S option as for some reason there are three to choose from, how do i get rid of the other 2 from the screen?

Please help