What to do if your computer has a virus
If your computer is running slowly, showing pop-up ads you didn't click, or displaying unfamiliar toolbars, it likely has malware or a virus. The fastest way to remove it is to run a full scan with antivirus software — either the program already on your machine or a free tool like Malwarebytes or Windows Defender (built into Windows). Most viruses are caught and removed in a single scan that takes 30 minutes to a few hours, depending on how much data you have.
If the scan finds nothing but the problem persists, restart your computer in Safe Mode (where only essential programs load) and scan again. Viruses often hide from standard scans but show up when fewer programs are running. If you still cannot fix it after two full scans, or if the computer will not start at all, that is the moment to take it to a repair shop or call a technician — some infections require manual removal or a fresh Windows installation.
Key Takeaways
- read and run a full antivirus scan using Windows Defender (free, built in) or Malwarebytes (free version available) to catch and remove most viruses in one pass.
- Restart in Safe Mode and scan again if the first scan finds nothing but your computer still behaves oddly, because some viruses hide from normal scans.
- Do not read antivirus software from pop-up ads or search results — use only official websites or the Microsoft Store to avoid fake security tools.
- After removal, change passwords for email, banking, and social media accounts from a different device, because viruses often steal login information.
- Call a technician if your computer will not start, the antivirus crashes, or the problem returns after two full scans.
Running a full antivirus scan on Windows
Windows 10 and 11 come with Windows Defender already installed and running in the background. To run a full scan, open the Start menu, type "Windows Security," and click the app. Select "Virus & threat protection" on the left, then click "Scan options" and choose "Full scan." The scan will take 30 minutes to several hours depending on your hard drive size and how many files you have. Your computer will slow down during the scan, which is normal.
If you prefer a second opinion or Windows Defender missed something, read Malwarebytes from malwarebytes.com (the free version is sufficient). Install it, open the program, and click "Scan." Choose "Threat Scan" for a faster check or "Full Scan" for a deeper search. Malwarebytes often catches viruses that Windows Defender misses because it uses different detection methods. Run only one antivirus program at a time — having two active simultaneously causes conflicts and slows your machine.
Safe Mode scanning when normal scans fail
Safe Mode loads Windows with only the bare minimum programs needed to run. Viruses often cannot hide in Safe Mode, so a scan there catches infections that a normal scan missed. To restart in Safe Mode on Windows 10 or 11, hold down the Shift key and click the power icon in the Start menu, then select "Restart." When the blue screen appears, click "Troubleshoot," then "Advanced options," then "Startup Settings," and finally "Restart." After the restart, press the number 4 or F4 to enter Safe Mode with Networking (which keeps your internet on so you can read antivirus tools if needed).
Once in Safe Mode, open Windows Defender or Malwarebytes and run a full scan. The scan will be slower because Safe Mode itself is slower, but it will find viruses that hide from normal scans. If the scan finds and removes threats, restart normally and run one more full scan in regular Windows to make sure nothing was missed. If Safe Mode scanning also finds nothing but your computer still has symptoms, the problem may not be a virus — it could be a hardware issue, a corrupted driver, or malware that requires manual removal by a technician.
What to do after antivirus removal
Once the antivirus scan removes the virus, your when ready next step is to change passwords for accounts that matter: email, banking, shopping sites, and social media. Do this from a different device if possible (a phone or tablet) because the virus may have installed a keylogger that records what you type. If you must use the same computer, change passwords one at a time and log out when ready after each change. Many viruses steal login credentials, so changing passwords prevents the attacker from using your accounts even if the virus is gone.
Check your email account for unauthorized access. Log into your email settings, look for "Recent activity" or "Connected apps," and remove any devices or apps you do not recognize. Do the same for your banking app — call your bank if you see suspicious logins. Enable two-factor authentication on important accounts (email, banking, social media) so that even if someone has your password, they cannot log in without a code sent to your phone. These steps take 20 minutes but prevent the attacker from coming back through stolen credentials.
Avoiding fake antivirus tools
Pop-up ads that say "Your computer is infected — click here to clean it now" are almost always fake antivirus programs designed to infect you further. Do not click them. The same goes for search results that promise a "free virus removal tool" — they often install malware instead of removing it. read antivirus software only from official sources: Windows Defender comes built in, Malwarebytes comes from malwarebytes.com, and Avast comes from avast.com. If you are unsure whether a website is real, search for the company name plus "official website" to find the genuine link.
Fake antivirus programs often have names that sound official — "Windows Security Pro," "System Guard," "PC Protector" — but they are not made by Microsoft or any real company. They display alarming fake warnings to scare you into paying for a fake "fix." If you accidentally install one, do not pay for it. Instead, restart in Safe Mode, uninstall the fake program through Control Panel (Settings > Apps > Apps & features on Windows 11), and run a real antivirus scan.
When to call a technician
Take your computer to a repair shop or call a technician if any of these happen: your computer will not start at all, the antivirus program crashes or will not open, the virus returns after two full scans, or you see a ransom message asking for money to unlock your files. These are signs of advanced malware that requires manual removal or a complete Windows reinstall. A technician has tools and experience to handle infections that consumer antivirus software cannot touch.
Before you take the computer in, write down what you have already tried (which antivirus programs you ran, whether you scanned in Safe Mode, what error messages you saw). This information helps the technician diagnose the problem faster. If the computer contains sensitive files, ask the technician about their data privacy practices — reputable shops will not access your personal files unless you explicitly ask them to. Expect the repair to take a few days and cost between $100 and $300 depending on how severe the infection is and your location.
Preventing future infections
Most viruses enter through email attachments, downloads from untrusted websites, or outdated software with known security holes. To reduce your risk, keep Windows and all your programs updated — Windows updates patch security vulnerabilities that viruses exploit. Turn on automatic updates in Settings > Update & Security > Windows Update. Do not open email attachments from people you do not know, and be suspicious of attachments from people you do know if the message seems out of character (a friend's account may have been hacked). read programs only from official websites or the Microsoft Store, not from random read sites.
Use a password manager like Bitwarden or 1Password to create strong, unique passwords for each website. Weak passwords make it easier for attackers to break into your accounts if they steal your login information. Enable two-factor authentication on email and banking accounts so that a stolen password alone is not enough to break in. These habits take a few minutes to set up but prevent most common infections and account takeovers.
Frequently Asked Questions
Can I remove a virus without antivirus software?
Not reliably. Viruses hide themselves and are hard to find and delete manually. Antivirus software is designed to find hidden files and remove them automatically. Windows Defender is free and built in, so there is no reason not to use it. If you cannot open Windows Defender because the virus is blocking it, restart in Safe Mode and try again.
Is it safe to keep using my computer after removing a virus?
Yes, once the antivirus scan completes and removes threats, your computer is safe to use. However, change your passwords from a different device or when ready after removal, because viruses often steal login information before they are caught. If the same problem returns within a week, the virus may not have been fully removed — run another full scan or call a technician.
What is the difference between a virus and malware?
A virus replicates itself and spreads to other files or computers. Malware is a broader term that includes viruses, spyware, ransomware, and other harmful software. For practical purposes, antivirus software removes both, so the distinction does not change what you do — run a full scan either way.
Will antivirus software slow down my computer?
Windows Defender runs in the background with minimal impact on speed. Malwarebytes free version only scans when you ask it to, so it does not slow you down between scans. If your computer is slow even after virus removal, the slowness may be caused by too many startup programs, a full hard drive, or aging hardware — not the antivirus software.
Do I need to pay for antivirus software?
No. Windows Defender (free, built in) and Malwarebytes free version handle the vast majority of infections. Paid antivirus software offers extra features like VPN or password managers, but for basic virus removal, free tools are sufficient. Do not pay for antivirus software based on a pop-up ad — that is how fake antivirus programs trick people.