The following is a true story from a few years ago.
A dad found a laptop on sale and bought it as a last minute Christmas present for his family. It was opened on Christmas day, and his son, little Johnny, immediately wanted to play with it. Unfortunately, within an hour or two of playing games on it, Johnny called to his parents and asked them to fix it. A ton of pop-ups and other items had gotten onto the computer. Even after restarting the computer, the pop-ups kept coming back.
I received a frantic phone call that night from their dad. He explained what had happened, and asked if I could fix it and “work my magic” on it. I did a factory reset, then added Computer Maintenance and Security items to it, including anti-virus and anti-malware programs, as well as ad blockers and updates to Microsoft and other programs. I also optimized the start menu so that it was running better than new. Upon returning the laptop to him, the father thanked me, and explained that they were planning on having me look at during the week after Christmas, but he never realized what could happen. Lesson learned. Be careful using a computer right out of the box. Make sure that you have it professionally setup.