The drivers that came along with my product was ofc only for Windows 8 since 8.1 wasn't released at the time of purchase.
But okay.. Neither HP nor Lenovo have any chipset/GMA-driver released yet, I am talking with HP so I hope they will make some kind of fix.
It was just, you know, a general issue on z2760 when updating to Win8.1 so I thought you guys perhaps was in some sort of dialogue with MS or something.
Check with your OEM now. There was recently a driver update released to OEM's that they should be distributing to users. Check the HP* website and see if the new driver update is available. If not, contact them directly and ask where it is
EDIT: Also, this driver is available via Windows* Update. Check there if your OEM does not have it as well.