Hi aliasger_jamali,
welcome to Questions & Answers..
Normally Vaio's come with a hidden HDD partition so as long as the Vaio your purchasing has the original HDD & that the recovery partition is still intact you should be able to restore your vaio back to original factory settings by doing the following..
To recover from the recovery area
On models with the ASSIST button
1 Press the ASSIST button while your computer is off to launch VAIO Care Rescue.
If the display language selection window appears, select your desired language and click OK.
2 Click Start recovery wizard.
To perform the custom recovery, select Tools and click Start advanced recovery wizard.
3 Follow the on-screen instructions.
On models without the ASSIST button
1 Turn on your computer and press the F10 key several times before the VAIO logo screen disappears.
If the Edit Boot Options window is displayed, press the Enter key.
If the display language selection window appears, select your desired language and click OK.
2 Select Start recovery wizard.
To perform the custom recovery, select Tools and click Start advanced recovery wizard.
3 Follow the on-screen instructions.
If the Vaio has a new HDD or the recovery partition has been formatted or is damaged then you could if you wish contact Vaio support & purchase a set of recovery disc's, which should allow you to restore your Vaio back to the supplies OS & pre-installed applications, etc.
Or depending on the model vaio you could purchase & install your own Windows OS & download the pre-installed drivers & utilities from the Vaio support site but unfortunately you can not download the pre-installed applications..
Hope this helps..