A new backdoor trojan can halt Windows even before the OS even completes the boot process.
New Backdoor Trojan Nukes Windows Boot Process : Read more
New Backdoor Trojan Nukes Windows Boot Process : Read more
fix = fdisk /mbr
Not necessarily accurate. If the system is still infected, repairing/replacing the mbr won't matter as when you boot back into windows it could just reinfect your system again.