Sony Vaio laptop Factory reset help pls

Hello,
I bought a Sony Vaio laptop with not installation disk but I would to factory rest it like new, only problem is with out the disk I feel hopeless in making this laptop mine, I know it will solve many of my problems at the moment Model number is: VGN-NR 498E
I have been at this for a month but would like to work with original factory setting to customize it as my own thanks if you do help me
-Ethan