Hi everyone I'm new here so I hope I'm doing this right.

I just bought a used DELL Inspiron 7000 laptop for my son. It did not come with an operating system therefore I bought a Windows XP system for it. The problem is that when you turn the PC on it goes to a black screen that says OPERATING SYSTEM NOT FOUND and I can't get it to do anything else. Please someone help me.
Thanks, Angie P