How to factory reset sony vaio desktop model vpcj1 ?

Acer Aspire ONE D255E
Type:Netbook OS: Windows 7 Starter HD: 250GB SATA DRIVE RAM: 1GB DDR3 CPU: Intel Atom 1.66ghz Wfi: YES WEBCAM: YES CHARGER: YES STATE: RE-furbished Manufacturer Defects NONE