Step-by-Step How-To · 6 min read
How to Scan a Windows PC for Viruses and Malware
Windows can perform a thorough malware scan with no additional software. Here is the exact sequence, from the fastest check to the most thorough one.
Published 2026-08-09 · Last updated 2026-08-09
Run a full scan with Windows Security
Press Start, type Windows Security and open it. Choose Virus & threat protection, then Scan options. Select Full scan and start it. A full scan reads every file on every attached drive and can take from twenty minutes to several hours depending on how much data you have.
- Start → Windows Security
- Virus & threat protection → Scan options
- Choose Full scan → Scan now
- Leave the PC on until it finishes
Run an offline scan if something persists
From the same Scan options screen, choose Microsoft Defender Offline Scan. Windows reboots into a minimal pre-Windows environment and scans before any malware can load. This is the single most effective built-in tool against rootkits and persistent infections, and it takes about fifteen minutes.
Get a second opinion
Install the free version of Malwarebytes, update its database and run a full scan. Because it is on-demand only, it will not conflict with your existing antivirus. It is particularly good at finding adware and browser hijackers that classical engines ignore.
After the scan
Quarantine or remove everything flagged, reboot, then scan again to confirm the machine comes up clean. Change passwords for important accounts from a different, known-clean device if you found anything that could log keystrokes.
Frequently asked questions
- How long does a full virus scan take?
- Typically 20 minutes to a few hours, driven by the number of files and whether you are on an SSD or a hard drive.
- Can I use the PC while scanning?
- Yes, though the scan will be slower and the machine may feel sluggish on older hardware.