Step-by-Step How-To · 5 min read
How to Install Antivirus Software Correctly
Most installation problems come from one mistake: leaving the previous antivirus in place. Work in this order and installation is uneventful.
Published 2026-08-09 · Last updated 2026-08-09
Step 1 — remove the old product
Uninstall any existing real-time antivirus from Settings → Apps, then reboot. If it resists, use the vendor's official removal tool — Norton Remove and Reinstall, McAfee MCPR, avastclear, AVG Clear, the ESET Uninstaller. Microsoft Defender needs no removal; it steps aside on its own.
Step 2 — download from the vendor only
Type the vendor's domain yourself rather than clicking a sponsored search result. Download portals and mirrors are a routine source of repackaged installers carrying adware.
Step 3 — read the installer
Choose custom installation where offered. Decline browser extensions, toolbars and optimisation add-ons you did not come for, and read the data-sharing checkboxes rather than clicking Next.
Step 4 — verify
Reboot, let the product update its definitions, run one full scan, and confirm in Windows Security that the new product is registered as your active antivirus provider.
Frequently asked questions
- Do I need to uninstall Windows Defender first?
- No, and you cannot. Windows disables Defender's real-time protection automatically when another antivirus registers.
- Why did my new antivirus fail to install?
- Almost always leftovers from a previous product. Run that vendor's official removal tool and try again.