If you know or suspect that your PC has been infected with any kind of malware, there are some very important precautions and steps that you need to take to minimize any damage to your data and privacy.

• Take the PC out of the network: If the PC is connected to the network via a network cable, then remove it to disconnect it from the network. If connected through wireless, disable the wireless adapter on your PC. This way, you can make sure that the virus cannot transmit any kind of information from your PC to other PCs or the outside world. This will also prevent the virus on your PC from causing damage to other PCs or data-storage on your network.
• Stop all the applications you are running: Some of the applications that you are using may be infected with the virus and cause damage.
• Try to reboot your PC in safe-mode: Just as it is rebooting, hitting F8 usually takes you to a list of boot options. Choose one of the "safe" options.
• Prepare to take a back-up: It would be best to connect an external hard-disk through a USB or Firewire port and back-up all your data. These would include some of the following areas, but there may be other things on your PC, depending on how you organize your data:
  • C:\Documents And Settings - This is where most of user data and application settings are stored
  • Other C:\ folders - For examples, you may have C:\tools or C:\Pictures or any such folder that were created by some software or by you. It is important to look carefully and make sure that you back-up all your data.
  • Other drives: You may have other disk-drives or partitions such as D:, E:, etc. Make sure that you back-up your data from those too.
  • There are folders like C:\Program Files which contain files related to software that you have installed. If you plan to re-install your PC completely, then these will get created when you install the software again. But if you have manually created any files in this area, you would need to back them up.
  • Operating system folders: C:\Windows, and such folders contain the operating system files. If you reinstall your PC, these will get automatically created. But again, depending on your usage, there may be files in there that you may want to back up. For example, if you had downloaded a particular file as a fix to a problem and copied it to some folder under C:\Windows, you would need to back up that file, just in case you need it after you reinstalled Windows.
• If you have any kind of back-up software installed, you can use it to copy all the above to an external hard-disk. But often it is advisable to just copy these manually using Windows Explorer in emergencies, so that you don't need to depend on any software on your PC since it is infected.
• Be patient while taking a back-up and make sure that you have copied all important data. When you are dealing with a PC crash or a virus infection, it is very common to feel stressed and rush to reinstall the PC. While doing so, you may lose important files if you are not careful. It is a good idea to write down all the folders that you need to back-up on a piece of paper, and keep checking these off as you copy them.
• If the copy action fails for whatever reason -- files being used by other applications, or destination disk going full, etc -- make sure that you repeat that copy until you get all the files.