Is My Windows PC Actually Infected?
How to Check Safely

“I think my computer has a virus” — let's find out for real

I hear that sentence almost every week, and here's what nobody tells you: most of the time, the computer is fine. What it has is a scary pop-up pretending to be Microsoft, browser notifications gone wild, or an ordinary slow afternoon. Scammers learned years ago that the fear of a virus is easier to sell than a real one is to write — the FTC has shut down “PC cleaner” operations that took over $100 million from people this way, and older adults are hit hardest.

The honest answer to “am I infected?” comes from a scan you start, using a tool you trust — and every Windows 10 and Windows 11 computer already includes one, free: Microsoft Defender, run from the Windows Security app. This page walks through the short version. The 25-page printable guide goes step by step, in large print, at kitchen-table pace.

First, the good news: that “virus warning” is almost certainly fake

A pop-up that says your computer is infected and gives you a phone number to call is a scam — every time. Real Microsoft error messages never include a phone number, and real antivirus alerts don't play sirens or robot voices. A web page can't actually scan your files; it's a poster of a fire, not a fire. Never call the number, and never let anyone who called you connect to your computer remotely. (This scam is big enough that I wrote it its own companion guide — the “Your Computer Has a Virus” Pop-Up scam guide.)

How to close a fake virus pop-up safely

1. Don't click anything inside the pop-up — even its own “Close” or “X” can be fake.
2. If the screen is stuck full-screen, press and hold the Esc key, then close the browser window.
3. If that fails, hold the power button until the computer turns off, wait ten seconds, and start it again. Nothing is harmed.
4. When the browser reopens, do not click “Restore pages.”
5. Then run a real scan (below) for peace of mind.

Stop the fake alerts sliding in from the corner of the screen

1. Those “Your PC is infected! (5 viruses)” boxes are usually browser notifications from a junk website that talked you into clicking “Allow” once. They're spam, not an infection.
2. In Microsoft Edge: three dots (⋯) > Settings > Cookies and site permissions > Notifications — then Remove or Block any site you don't recognize.
3. In Google Chrome: three dots (⋮) > Settings > Privacy and security > Site settings > Notifications — same cleanup.
4. From now on, when a site asks to “show notifications,” the safe answer is Block.

What a real infection actually looks like

• Your browser's home page or search engine changed itself, or toolbars appeared you didn't install.
• Programs you never installed show up, or security settings turn themselves back off after you turn them on.
• Friends get strange emails or messages “from you” with links.
• Passwords stop working, or reset emails arrive that you didn't request.
• The machine is frantic — fan roaring, everything molasses-slow — even after a real restart, while you're doing nothing.
• Notice what's not on this list: a pop-up announcing a virus. Real malware hides. The fakes yell.

How to run a real scan — free, already on your computer

1. Click the Start button and type windows security, then open the Windows Security app (the blue shield).
2. Click Virus & threat protection.
3. Click Scan options, choose Full scan, then Scan now.
4. It takes an hour or more and you can keep using the computer — or go do something pleasant.
5. “No current threats” means exactly that. If it finds something, Defender quarantines it — that's the system working, not failing.

Still uneasy? Two deeper checks, both from Microsoft

For stubborn worries, run the Microsoft Defender Antivirus (offline scan) from the same Scan options page — it restarts the computer and inspects it before Windows fully loads, so clever malware has nowhere to hide (about 15 minutes; save your work first). And for a second opinion, download the free Microsoft Safety Scanner — only from a page ending in microsoft.com. What you should never do: click a “free virus scan” ad, or install a paid “PC cleaner.” Those rigged scans “find” hundreds of problems on every computer, including brand-new ones — that's the product.

When to get help

Handle it yourself: closing fake pop-ups, clearing notification spam, running scans. Call me — or any tech you trust — when scans keep finding things, symptoms outlast a clean scan, someone had remote access to the machine, or you already paid someone and want company working the bank-call checklist. No lectures here, ever. It's a $99 flat visit with a 30-day follow-up, anywhere in Portage County.

What's in the 27-page PDF

• The fake “virus detected — call now” pop-up: how to spot it and close it calmly
• Browser notification spam — how one “Allow” click causes weeks of fake alerts, and the 2-minute fix in Edge and Chrome
• Real infection red flags vs. normal computer quirks — a side-by-side reference table
• Windows Security step by step: opening it, and running Quick and Full scans
• The Microsoft Defender offline scan — the restart-first deep check, demystified
• Reading your results: quarantine, Protection history, and what “PUA” really means
• A safe second opinion with Microsoft Safety Scanner — and the “free scan” ads to never click
• Task Manager without the fright: what those strange process names actually are
• Why paid “PC cleaner” and “registry fixer” apps are a racket — and how to uninstall one
• What to do if a scan finds something, step by step — including the password-change order
• Already called, clicked, or paid? The first-hour and first-week damage-control checklists
• A monthly 15-minute peace-of-mind check-up, a kitchen-table FAQ, a plain-English glossary, and a fill-in cheat sheet

Why I wrote this

Half my “virus” house calls end with me removing the so-called cure — a paid cleaner app — instead of an actual infection. That bothered me enough to write it all down. The tools that give you a real answer are free and already on your computer; what people are missing is a calm walk-through and permission to stop worrying after a clean scan. That's what this guide is. I print these as large-print handouts, and my scam guides double as handouts for senior-center talks around Portage County. — Bill