I can't tell you for certain what they will have done but it is along the lines of power saving tricks to only use graphics acceleration when it is actually necessary to extend laptop battery life. The end result is that the stock hardware driver from the graphics chip maker almost invariably will not work correctly on a bespoke laptop graphics implementation. How it manifests is either BSOD or refusing to load.
But don't take my word for it - here is the relevant Intel page:
The HD graphics 4600 should be a lot more capable than that. What CPU and clock speed are you running?
Try running GPU-Z and/or a couple of proper graphics benchmarks and see what they reveal? GeekBench and PassMarks performance test for instance.
It may be that you need to disable the non-functioning NVidia graphics card in the bios to allow the Intel driver to run flat out or something.
Lenovo portables are the old IBM brand cheapened down and plasticised. Not the greatest but reasonably competent.