We need more clues than what you're giving... What does this image look like and when do you see it?

Did YOU reinstall Windows XP? Did you install the latest service pack 3 as well? Did you also install all the correct hardware drivers? (Such is required because the XP installation won't do that for you.)

Have you scanned the computer using a spyware removal tool such as Malwarebytes, or something similar.

Hope this helps and let us know more.