
  This is an attempt to ask a canonical question as discussed in this old meta post. The goal is to create something helpful that can be used as a duplicate when non experts ask about virus infections. 


Let's say that I have determined beyond doubt that my home PC is infected by a virus. If necessary, you can assume that my computer runs Windows. Answers aimed at the non-technical reader are encouraged.


What do I do now? How do I get rid of the virus?
Do I really need to do a full reinstall? Can't I just run a couple of anti-virus programs, delete some registry keys, and call it a day?
I really don't have time to deal with this right now. Is it dangerous to keep using the computer while it is infected?
I don't have backups of my family photos or my master thesis from before the infection occurred. Is it safe to restore backups made after the infection occurred?
Do I need to worry about peripherals getting infected? Do I need to do anything about my router or other devices on my home network?



What do I do now? How do I get rid of the virus?

The best option is what is referred to as "nuke it from orbit."  The reference is from Aliens:

The idea behind this is that you wipe your hard drive and reinstall your OS.  Before you do this, you should make sure you have the following:

A way to boot your computer off installation media. This can be in the form of the Install CD that came with your computer, or a DVD you burnt from an ISO file (Windows can be downloaded legally here). Some computers do not have CD-ROM drives anymore.  Microsoft provides a tool to convert their ISO files to bootable thumb drives. Do not create the install media on the infected computer.
Your Original Windows License Key. This can either be on a sticker on the side of your computer or you can recover it from your computer a program like The Magical Jelly Bean Keyfinder (which might contain malware, but it really doesn't matter because you are wiping it all after you get the key anyway). Or an official tool supplied with Windows called slmgr.vbs.
Drivers. If you don't have a second computer, you are really going to want to have at the minimum video drivers & network card drivers.  Everything else can be obtained online after you reinstall.
Any files you want to save.  You can back them up to a thumb drive for now, and scan them before putting them on your freshly installed machine (see below).



Do I really need to do a full reinstall? Can't I just run a couple of virus programs, delete some registry keys, and call it a day?

In theory, it is not always necessary to fully reinstall. In some cases you can clean the virus off the hard drive without a full reinstall. However, in practice it's very hard to know that you have gotten it all, and if you have one virus it is likely you have more. You might succeed in removing the one that causes symptoms (such as ugly ad popups), but the rootkit stealing your password and credit card numbers might go unnoticed.
The only way to kill everything is to wipe the hard drive, so your best option is always to nuke it from orbit. It's the only way to be sure.


I really don't have time to deal with this right now.  Is it dangerous to keep using the computer while it is infected?

You may not have time for it right now, but you really don't have time for your email getting hacked and your identity being stolen. It's best to take the time to fix it now and fix it right before the problem gets worse.
While your computer is infected all your keystrokes might be recorded, your files stolen, it might even be used as a part of a botnet attacking other computers. You do not want this to be going on for longer than necessary.
If you really don't have time to deal with it right now, power down the computer and use another one until you have time to fix it. (Be careful with file transfers from the infected to the uninfected computer, though, so you do not contaminate it.)


I don't have backups of my family photos or my master thesis from before the infection occurred.  Is it safe to restore backups made after the infection occurred?

Any backups made after the virus infection occured could potentially be infected. A lot of the times they are not, but they could be. Since it is very hard to pinpoint exactly when the infection occured (it may be before you started to notice symptoms) this applies to all backups.
Also, Windows restore points can be corrupted by a virus.  It is better to archive copies of your personal files on external or cloud storage.
If you are restoring them from external or cloud storage on a computer that has already been nuked from orbit make sure you scan all the files you are restoring before you open them. Executable files (such as .exe) can contain viruses, and so can Office documents. However, picture and movie files are likely safe in most cases.


Do I need to worry about peripherals getting infected? Do I need to do anything about my router or other devices on my home network?

Peripherals can be infected.  Once you have re-installed your OS you should copy all the files off your thumb drive, scan them with antivirus, format the thumb drive, and restore the files to the thumb drive as needed.  Most routers will be fine, however, it is possible for DNS settings to be compromised either through a weak password or malicious use of UPnP.  This can easily be resolved by resetting the router to factory defaults.  You may also want to configure your DNS settings to either google dns or OpenDNS. If you have some type of network attached storage, you should do a full scan of it with antivirus before using any of the files on it.
See Also: Help! My information has been stolen! What do I do now?
THIS IS WORKING DRAFT FEEL FREE TO WIKI/EDIT AS NEEDED
