I write this article inspired from various people that have operating system booting problem cause of virus.
When Windows doesn’t start in normal or safe mode the only solution isn’t the format.
You can do it in 3 ways:
Use a live cd there are antivirus bootable cds tha allows make scan so without being on Windows operating system, the cons is that when the definitions are updated you must download and burn a new disc image. You can find the best free antivirus bootable rescue cd here:
Raymond
Digital Citizen
Lifewire
Connect hard disk to another computer if the hard disk is 3.5 inch SATA, PATA, IDE is possible to connect to another computer internally as an extra hard disk or externally via USB within an adapter and make scan with own antivirus installed. If the hard disk is 2.5 inch (of the notebooks) you can connect it externally via USB within the adapter.
Restore image with a bootable cd if you already have a system image saved you can restore last backup state within a bootable cd of the clone programs (some have this feature)