If you are using Office or any of it's components, such as Word or Access, you may need to input a product key into the program to get it to operate. However, the product key may have been a trial offer good for a set amount of time. That trial period may have run out. If this is a brand-new PC, as in you purchased it a few days ago, you may need to call the manufacturer to get a valid trial key. Alternatively, you could use OpenOffice
if you need a word processor immediately.