How to restore factory settings on Inspiron N5010

hi guys,

i've got a Inspiron N5010 with Win 7 home but the OS got crashed. i've been trying to restore it to factory settings & tried to boot up and press F8 and then enter 'repair windows', but its again stucks to a blank wallpaper page with no options. It doesn't have any options of how to restore the machine.

also i haven't got any reinstallation DVD / CD with with this model.

Can anyone help how can i get this OS for reinstallation or any other way to restore my system back

thanks