hi. i am new in this forum. recently my pc has started malfunctioning. windows will not boot! when i enter setup (bios) i cant see my hdd. sometimes its there and sometimes not! when i boot to repair disk (when the hdd is detected) and run startup repair it shows like this : "root cause found : the partion table does not have a valid system partition". and sometimes (when hdd is not detected) it shows: system repair cant resolve this issue. in diskpart i cant see my drives. anyway i decided to run super fdisk to correct my partion table. but when i boot to it, it does not detect a hdd. also i did a change in the bios (which looks like has screwed my pc) i changed the sata controller from ACHI TO ATA. but when i tried to restore defaults (default is ACHI) it does not detect my hdd. and also ones i was in my repair disk and from there i opened cmd and then regedit. then i opened FILE->IMPORT (to see my drives which usually cant be seen) and i COULD SEE ALL THE PARTITIONS! but i cant see the system partition. i was also able to browse files on other partitions but not the sys partition. currently i have a cd with super fdisk loaded. ready to boot. but cant see my hdd. what to do? have i screwed up my pc with that change in bios? if so, wat to do?