Hang up on booting up

[dybdahl]

Alright,

 

System:

CPU I5-4670k

MOBO - MSI Z87-gd65

Ram - Kingston hyper x Predator

Power Supply - EVGA 2400 watt

Cooler - Cooler Master H100i

OS - windows 8.1 pro / windows 10

Graphics - 2x Sapphire 7990

 

recently i have been getting hung up on the login screen when trying to boot my computer, it would also restart ranomly sometimes too. I replaced the harddrive thinking that could be the problem and it wasnt. It would run better with one 7990 installed for a long time, and now it doesnt seem to matter if i have them installed or not. The other weird part is that it boots and run just fine with the on board graphics. i have tried both graphics cards in different slots and it doesnt change the result. I have done memory tests already and no errors came up. I have done system scans, icacls.exe, and nothing. mind you, i have nothing installed other that the OS and drivers. if any of you have any idea what it could be.

 

Derek