format saja..
use bootable usb or if can access windows repair setting go reset pc (it's similar to format, but can choose option keep personal files)
done ez peasy

if liddat, use bootable usb lah
use this method, i'd say bye2 to personal file
but need another pc for this lah, use other pc if u hab or ask frend for help/borrow
-prepare min 8gb usb stick
-go windows 10 website, dolod the Create Windows 10 installation media tool
-once dolod, use the tool to make usb bootable device..just folo instruction from the tool
-wait finish, then boot ur pc with the usb and then folo instruction saja
easy peasy peanut bater kachang kulet kuda

if want sabe personal file, then bcum extra leceh
take hd out, connect to other pc, copy paste data
after that only format the hd

yes
plug into other pc either externally or as extra internal hd (secondary, tertiary or whatever)