Hello I was just curious as to if there was a way to prity much replace windows files with new one VIA command prompt or something without getting into windows. What im thinking of is lets say I have a virus, and it wont let me go into windows. Can I just copy windows files from a fresh windows install into the proper folders and it will remove the virus and still let me keep all my programs and data safe? Instead of having to reinstall windows?
Most of times it wont work this way, but sometimes it might work by replacing some of the system files (not recommended). Because you do not know which part of the OS is infected, the best practice is to boot your system in Safe Mode, obtain a copy of Malwarebytes in some flashdisk, install it and clean in Safe Mode. Alternatively you can use Recovery console by inserting installation disk in drive. I had same trouble many times but the method you talked about is bruteforce and cant be applied over all kind of infections. Hope it helps.
Most viruses damage the registry files. That's where the "this program is installed" information is kept. If you replace the registry files, your programs are no longer installed. If you don't, the damage is still there. You can do a repair install of Windows, which reinstalls the Windows files themselves, but doesn't change the registry, so your programs are still installed. Since there are different ways of doing that for different versions of Windows, see this page for links. If the registry is damaged, there are many programs that can clean most of it up. See CCleaner.