This fault is either a driver problem or a memory problem. Check with your motherboard maker for BIOS updates; try different ram or only one stick even though your memory passes the memory tests.
By the way what a rubbish motherboard if it doesn’t let you disable the onboard sound and network adapters get another one if you can’t resolve this problem.
It probably is but the problem is it is a fairly new laptop and i can't open the memory bank as it will void the warranty. The BIOS is Insyde H20, no way of modifying anything, likely per Sony''s demand. Anyway, I will wait to see if other people with Vaio z590n laptop have similar problems. Thanks.