A "Finding Dory ad" doesn't sound right. Did that really happen without installing something dodgy??
Sounds like the Windows Spotlight "feature" at work:
http://www.howtogeek.com/243263/how-to-disable-ads-on-your-w...
With OEM Windows, everything can be expected, from bloatware "drivers" slowing down your machine by half to obligatory root certificates (thanks Lenovo! thanks DELL!) that are necessary to serve you in-browser ads. And you're not theoretically allowed to remove them or it voids you warranty. So an ad at startup doesn't surprise me, it's not really Microsoft's fault, but that's what you get with a Windows OS.
https://www.extremetech.com/computing/218437-dell-laptops-ma...
I'm fairly certain that its Microsoft that was responsible for this. Others have reported it as well.
https://www.reddit.com/r/assholedesign/comments/5e7kwl/windo...
I feel like paid $199 just so Microsoft can sell me to advertisers. Bill never would of stood for this shit.