Most "slow" computers aren't broken — they're bottlenecked on one specific component. Four upgrades that produce the biggest real-world speed improvement, in priority order.

1. Swap the hard drive for an SSD (~$40-80)

The single biggest upgrade you can make to any computer built before ~2018. A mechanical hard drive replaced with a solid-state drive turns a 5-minute boot into a 15-second boot; applications open instantly. Clone the existing drive using free software (Macrium Reflect, Clonezilla) — no OS reinstall required.

2. Max out the RAM (~$30-80)

Most old computers came with 4-8 GB; modern usage (browsers, Office, Zoom) wants 16 GB minimum. Check your laptop model for maximum supported RAM and buy accordingly. Installation is typically one panel screw and a 5-minute module swap.

3. Fresh OS install or major cleanup (free)

Years of software installation/uninstallation leave cruft. Either clean reinstall of Windows (Windows 11 is free if you had a licensed Win 10 on the machine), or an aggressive cleanup: Autoruns for startup programs, CCleaner for registry, bulk uninstall of unused applications.

4. Replace the battery (~$30-50)

A degraded battery doesn't slow the computer, but it makes it annoying. Original equipment is cheap on eBay; replacement is usually 5 minutes if the battery is user-serviceable.

What NOT to upgrade

• The CPU — usually soldered on laptops, not worth the effort on desktops unless the motherboard supports a significantly better chip.
• The GPU on an integrated-graphics laptop — not physically possible.
• The screen — fixable if broken but doesn't address speed.

The cost-benefit math

Total: $100-200 for all four upgrades. Result: a 5-8-year-old computer that feels like a new midrange machine. New midrange machine would be $600-800. Worth doing.