Why is my laptop have a black screen with a blinking white curser

[LINDA KELLY]

i did a system restore on my sony laptop now there is a black screen with a blinking curser

 

[LINDA KELLY]

i don't have the operating system with installation cd bought the laptop used didnt come with the cd

 

[LINDA KELLY]

Have you Created Restore Point of your Computer ?

no because it wont let me it stays at the black screen