I had blender 2.78 installed on my pc working greatly on windows 8. But as soon as I updated my window to windows 10, blender shows me this error "Blender - Can't detect 3D hardware accelerated driver!". I know I can install openGL 2.1 and its not a big issue, but I want to know why this error occurred only when I updated my windows? Thank you.
There does not seem to be one satisfying explanation about why this happens when you update Windows. This is just something that happens sometimes when updating Windows - stuff breaks sometimes. Microsoft is a company, people work in it, people make mistakes. Something just went wrong during the update.
Also one does not install OpenGL. OpenGL comes as a part of your graphics drivers instead, so you can update the graphics drivers. Updating the graphics drivers should be the first thing to do when you get an error message like that from Blender.
Report such issues to Blender developers as yours is yet another post here about problems with Blender on Windows 10. Perhaps they should drop Microsoft guys a word. It seems downgrading/not upgrading Windows is the only way out of this for the time being.