My partner's computer is a months-old laptop that came with Win10 Home. She's had problems with full-screen videos for almost its entire lifespan, though the problem did ease off for a while before returning in full force. When playing videos full screen, the videos will skip or slow and the computer will begin running slow, often to the point of totally freezing. There's no known single trigger as she often has nothing open at the time. This appears to happen irrespective of the program used - Chrome and Edge both have the issue, as does WMP for offline videos.

The machine is a Dell XPS 15 which has had no hardware modifications, so it's running an Intel Core i7, NVIDIA GeForce GT 750M, 16GB of RAM, and an unknown mainboard. We've tried updating all video drivers to no avail. I suspect a software issue but I've got absolutely zero clue where to start looking.

Any ideas?