Buying Advice · 5 min read
Antivirus for Older and Low-Spec PCs
On a machine with 4 GB of RAM and a mechanical hard drive, the wrong antivirus is the difference between usable and unusable.
Published 2026-08-09 · Last updated 2026-08-09
Lightest realistic options
Microsoft Defender, ESET and Webroot are the three that consistently behave on constrained hardware. Defender has the advantage of already being there. Webroot's client is unusually small because classification happens in the cloud.
What to avoid
All-in-one suites bundling optimisation utilities, VPN clients, browser extensions and update services. Each adds a background process, and on a 4 GB machine that adds up quickly.
Settings that reclaim performance
Schedule full scans for a time the machine is on but idle, and rely on real-time protection in between. Disable in-product marketing notifications. Reduce startup programs in Task Manager — on old hardware that usually helps more than changing antivirus.
The uncomfortable truth about unsupported Windows
If the PC runs a Windows version that no longer receives security updates, no antivirus makes it safe. Unpatched OS vulnerabilities are exploited directly, below the level where a scanner helps. Upgrade the OS or move the machine off the internet.
Frequently asked questions
- What is the lightest antivirus?
- Webroot and ESET among paid products; Microsoft Defender among free ones, since it is already part of the OS.
- Will antivirus fix a slow PC?
- Only if malware is the cause. More often the cause is a hard drive, low RAM or too many startup programs.