Pornographic photos found in computer files

Hello,

One day, I was on my friend's computer and I accidentally stumbled upon pornographic photos.

He, who is well-versed in computers and plays a lot online, told me he didn't know where they could have come from and swore that he had nothing to do with it, that these images had downloaded themselves onto his computer because when he downloads, a lot of porn ads pop up.

I have to admit that I don't know much about all this, which is why I'm asking you if it's really possible that these photos came from the Internet and not from my friend.

The photos were in the data disk, games directory, Bioware, globalization, and then a bunch of files with naked women.

Thank you for enlightening me.