OK folks, I'm not sure how widespread this might be.
I am looking at a GeForce 210 assembled by Asus (and I like Asus video cards). The OS is Vista (Home Premium) and we have a bog standard AMD Sempron 145 + 4GB DDR2 800MHz et cetera....
The latest updates from Microsoft and NVIDIA themselves fail when you try to play a video. The OS loads just fine, and works OK.............video freezes to a blank screen.
The solution is to reload the drivers/software from the CD or the manufacturer's website.
Sorry for the 101 fault finding post, but this sort of problem with NVIDIA is pretty much unheard of in my experience.