I'm running a laptop with a sandybridge i5 and an optimus setup and both video card drivers load and then before the login screen appears they error out and give error code 39. I have a machine at work that is doing the same thing and it has an nforce chipset with a nvidia 8xxx series chip. The current solution is the #1) never reboot, and #2) when windows forces you to reboot, simply reboot and uninstall the drivers after windows loads without deleting the drivers. The rescan the hardware from the device manager and they just reinstall and work like nothing ever went wrong. Both of these machines were upgraded from Windows 7, but I don't think it makes a difference. I've tried the beta intel drivers for windows 10, the beta nvidia drivers for windows 10, the stock windows drivers, the windows 8 drivers. All do the same thing. Sometimes when I reboot, they magically don't dump after almost giving the login screen. This is the only real problem I have had left now. I managed to clean up the mess that the widows 7 installations were in. Both machines now pass SFC. I had to rebuild the hives. I'm really reluctant to toast my installations and start fresh as I have a lot of things installed and such that would be a major pain to set back up again. Also to go through all that and have potentially the same exact problem wouldn't be exactly cool. This doesn't seem to be as widespread so I'm really puzzled what's going on with my machines. Anyone have problems with this?