registry blocks windows start up

my pc last days crashed due to cpu overheat and windows did a disk check at start up.for many reasons i wanted to get rid of CHKDSK and in a microsoft website they said i had to change something in registry.unfortunately after i messed up with registry my windows stucks on startup page(windows is loading...).when i start windows repair by pressing f8 it loads windows files and i see a blue screen(Like this in welcome page) but nothing else appears.i tried to format windows and the same happens.nothing appears except welcome blue page.the prob is at BIOS?

Hello nick and welcome to Seven Forums.

Were you able to find out the cause of the CPU overheating? If that problem remains your computer may crash again.

If you're not sure what all was changed in the registry, I'd go straight to a Repair Install.

Repair Install

every summer my cpu overheats so its something normal for me.thats why i dont play pc games these months.CHKDKS failed to continue and stucked because one of my hard disks is not working well.whatever, i cleaned cpu fan and the temperature prob is solved but registry prob still blocks my format.my HDDs are fine except last one

now about registry,thats what i did :
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager
in the right hand pane, double click BootExecute.
The default value of the key is autocheck autochk *
* means every drive is checked for consistency. Just add /K:C at the end before *. /K switch will disable autocheck on C: drive at Windows startup. So the final value should look like this:
autocheck autochk /k:C *
i did the same with the rest 2 drives i had,so i disabled them all

then i reboot and it worked.but next time i opened pc my windows stucked in startup page.i tried to repair or format windows by usb but nothing loads except blue screen i mentioned last time
sorry about my bad english and thx alot