White text box stuck on desktop screen

Hi

I have a small text box stuck onto my desktop screen- like the one you would find under a doc that you had saved to the desktop - but theres no doc with this one. It is fixed - can't open it, click on it, cut or paste/copy - nothing!! Its stuck in centre of my desktop with -ba e ticket at email ba com- written in it.

Any ideas on how to get rid of it please!!