I have an Alienware m15 with i9 8950HK processor. After motherboard replacement I didn't reinstall Windows and I can't change the voltage offset and overclock my CPU using Intel xtu. How can I fix this?
Uninstall XTU and do not reinstall it. If your device has some dell/alienware utility for overclocking, uninstall it.
Contact dell after you do this and ask them for support on their bios and reset/default settings.
Also, what version of W10 are you using? 1909?
"I already deleted Intel XTU". I hope you meant "Uninstalled".
Reinstall Windows 10, and do not use XTU ever again. You may be able to get away with doing a Windows RESET.