When I was a kid, the first PC I built was a white box with a Pentium 4 HT, which was still a fairly new CPU at the time. It ran hot so I cut a hole in the side of the case, bolted a 120 MM fan in the hole, and covered it with a shroud that I think I must have fabricated with Aluminum facia.
It didn’t look pretty but it worked. And it kept my bedroom toasty in the winter.
I mean, that’s essentially how my first tower PC was cooled. Bought it as a complete PC and the cooling was a blower style fan that sucked cool air through vents on the side via a plastic shroud.
And it was also one of the wonderful pentium 4 space heaters with incidental compute.