Downloading any kind of files from a torrent site can be risky. Malicious users often package malware with popular files and attempt to circulate it through torrents. Malware is usually disguised as recent music or movies that the most people are searching for and downloading. The expected files may not even be included in the download, or they may be there alongside the malicious software.
Be suspicious of any .exe files included in a download that is supposed to be music, movies or other data formats. There is no reason for executable files in this situation -- only the data files themselves, usually within a compressed archive. Make sure your file explorer program is set to display the full file extensions so you can see what kind of file you're actually working with. Many malicious files are named something like "example_song.mp3.exe," which is actually an executable file, not an MP3 file.
Your computer needs to have one actively running anti-virus program that is kept up-to-date. More than one can sometimes cause problems. A very effective and free anti-virus program is Microsoft Security Essentials (see Resources.) It will keep itself up to date, scan downloads and function properly in Safe Mode. ESET provides a free, one-time, online scan through a Web browser. The anti-virus you run ideally needs to remain active in memory, scan downloads and function in Safe Mode. AVG, Avast and BitDefender all have free editions of their antivirus products.
To properly attempt to rid a Windows computer from a virus, you will need to run a full scan from within Safe Mode. Make sure your anti-virus definition files are up-to-date and reset the computer normally. Immediately after it starts up, tap the "F8" key and continue to tap it until a Safe Mode menu comes up. Choose "Safe Mode Without Networking" with your arrow keys, and hit "Enter." The computer may take a while to boot to desktop in this very minimal mode, and at a very low resolution, but most malicious software will not be loaded here. Do a complete scan with your anti-virus software, and choose to quarantine and remove any malicious files found. Reset the computer afterwards, and then run a full scan again from inside a normal boot of Windows.
Format and Reinstall Windows
Unfortunately, any number of scans may not solve the problem. Some particularly bad root-kits and trojans are almost impossible to remove with any antivirus software. Attempting to remove them may even leave the Windows installation in a damaged state afterwards. In these instances, or to be absolutely certain the malware is off the computer, the only effective option is to format and re-install Windows. Most computers these days come with a restore partition on the disk and can be formatted and recovered to factory state easily, or you may need a Windows install disc. The downside is complete loss of all data that was not backed up, but you can be sure the malware is off for good.
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