Slow Computer Fix: How to Speed Up a Windows PC

A slow PC isn't just annoying. Multiply five wasted minutes per person per day across a 30-person business and you've lost the equivalent of one full-time employee, every year, to spinning loading icons. This guide walks through what actually makes Windows 10 and Windows 11 slow, and the fixes that work, in priority order.

The fastest wins (under 5 minutes)

If you only do three things, do these:

1. Restart properly. Not "shut down lid → reopen". A full restart from the Start menu. Windows quietly accumulates stuck processes and memory leaks; a real reboot clears them. Do it weekly minimum.
2. Close browser tabs. Chrome and Edge are the single biggest cause of "my laptop's slow" on modern UK office machines. Each tab is a process. 30 tabs = 30 processes fighting for memory. Use a tab manager or just be honest about which 30 articles you'll never read.
3. Check Task Manager.Ctrl+Shift+Esc, click the Performance tab, then the Processes tab. Sort by Memory and CPU. If something you don't recognise is using 50%+ of either, that's where the problem is.

If those three didn't fix it, work down the list below in order.

Find out what's actually slow

"Slow" means different things. Diagnose properly:

• Slow to boot, too much starting on login. Skip to Disable startup programs.
• Slow once running, usually RAM or CPU pressure. Skip to Memory and CPU.
• Slow when saving / opening files, likely the disk. Skip to Storage.
• Slow only on the internet, that's not your PC. See no internet access fixes.
• Slow only in one app, that app needs reinstalling or updating, the rest of Windows is fine.

Disable startup programs

Half the apps on a corporate PC silently launch at boot, Teams, OneDrive, Adobe Creative Cloud, Spotify, Slack, Discord, six different "helper" utilities from printer drivers. Each adds seconds to login and steals RAM forever after.

1. Ctrl+Shift+Esc → Startup apps tab (Win 11) or Startup (Win 10).
2. Sort by Startup impact.
3. Disable anything marked High that you don't need on login. Safe to disable: Spotify, Discord, Skype, Adobe updaters, manufacturer "support" tools, OneDrive (if you don't sync at boot), iTunes, Java updater.
4. Don't disable: antivirus, your VPN client, Microsoft Teams (if your business uses it for calls), security agents your IT team installed.

If unsure, ask your IT support before disabling anything corporate-looking, some agents are mandatory under your cyber security policy.

Free up disk space

Windows behaves badly when the system drive is over 90% full. SSDs in particular slow to a crawl when nearly full because they can't manage wear-levelling efficiently.

Quick wins:

1. Settings → System → Storage → Cleanup recommendations. Empty Recycle Bin, clear Downloads, remove old Windows update files (often 20+ GB).
2. Storage Sense, turn it on to auto-clean temp files and emptied Recycle Bin every 30 days.
3. Uninstall apps you don't use, Settings → Apps → Installed apps, sort by size. Old games, three different PDF readers, that screen-recording trial, gone.
4. Move large folders to OneDrive or an external drive. Photos, video projects, archives.

A modern Windows install needs about 30 GB free as breathing room. Less than that and you'll see slowdowns no amount of tinkering can fix.

Memory and CPU

If Task Manager regularly shows Memory at 90%+, you're under-spec'd for what you're doing. Two options:

1. Use less memory. Close Chrome tabs, exit apps you're not using, restart Outlook (it leaks memory over the day), avoid running multiple browsers at once.
2. Upgrade RAM. A laptop with 8 GB will struggle with modern Microsoft 365, Teams calls and a browser session. 16 GB is the realistic minimum for office work in 2026; 32 GB if you do design, video or development. RAM upgrades are one of the cheapest performance wins available, typically £40–£80 for an SODIMM that doubles your machine's capacity.

CPU is harder to fix without replacing the machine. But check what's actually using CPU, antivirus scanning, Windows Search indexing, OneDrive sync of a huge folder, or a runaway browser tab can all hammer the CPU temporarily.

Storage: the single biggest performance upgrade

If your business PC still has a mechanical hard drive (HDD) instead of an SSD, that is the single biggest reason it's slow, and replacing it will feel like getting a new computer.

How to check: Task Manager → Performance → Disk. If it says "HDD", you have a mechanical drive. If it says "SSD" or "NVMe", you're already on solid state.

A 500 GB SSD costs around £40. The labour to clone the existing drive and swap it is typically 1–2 hours. The boot time goes from 60+ seconds to 10. Apps open instantly. The machine feels 5 years younger.

This is a standard upgrade we do for managed clients all the time, and refusing to upgrade a 7-year-old PC is almost always a worse business decision than just buying a new one. See our IT consultancy on when to refresh vs upgrade.

Update Windows and drivers

Out-of-date Windows is slow Windows. Updates fix performance bugs, security holes and driver compatibility.

• Settings → Windows Update → Check for updates. Install everything pending. Restart.
• Update graphics and chipset drivers from the manufacturer's website (Dell, HP, Lenovo, etc.), Windows Update doesn't always push the latest.
• Don't pause Windows updates indefinitely. A common "fix" suggested online is to pause updates because they slow the PC; this is the opposite of what you want long-term.

Run an antivirus scan

A genuinely slow PC that wasn't slow last week may be infected. Cryptomining malware, in particular, sits quietly hammering the CPU.

Run a full scan with Microsoft Defender (built into Windows 10/11) or your business antivirus. If your IT support uses something like Bitdefender or SentinelOne, ring them and ask for a full scan from their console.

If you find something, don't just remove it and move on, escalate to IT support. Where there's one infection, there's often more, and you may need to assess whether your data has been exposed.

Power settings (laptops especially)

Many corporate laptops ship in Balanced or Battery saver mode. That throttles the CPU and feels slow.

• Settings → System → Power & battery → Power mode → Best performance when plugged in.
• Check the manufacturer power utility (Dell Power Manager, Lenovo Vantage, HP Command Centre) for additional performance modes.
• If you regularly work plugged in, set the laptop to never sleep when on AC.

Reset, don't reformat

If you've worked through this list and the PC is still slow, the Windows install is probably full of accumulated cruft. Don't reformat from scratch, use Reset this PC.

Settings → System → Recovery → Reset this PC → Keep my files.

This reinstalls Windows but keeps your documents, then prompts you to reinstall apps. It takes about an hour and fixes 95% of "old PC feels slow" issues without losing anything.

Before doing this, back up everything important to OneDrive or an external drive. "Keep my files" usually works but "usually" isn't "always".

When it's time to replace, not fix

Some PCs are beyond saving:

• Boot time over 2 minutes even after cleanup. The machine has reached the end of its useful life.
• Less than 8 GB RAM and you can't upgrade. Modern Microsoft 365 needs more.
• Pre-2017 CPU. Won't support Windows 11, security updates ending soon.
• HDD that can't be replaced (some ultrabooks).
• Repair cost is over 50% of replacement.

A fleet of 5-year-old PCs costs more in lost productivity than the savings from delaying replacement. We do refresh planning for clients as part of our IT consultancy service, modelling the actual hourly cost of waiting vs the cost of new kit usually makes the decision easy.

Quick reference

The honest version: most "slow PC" problems are fixable in under an hour. The unfixable ones are a sign that the kit has aged out of usefulness and is now costing you money to keep limping along. Either way, your business shouldn't be losing hours a week to slow computers in 2026, see our IT support for what proactive maintenance and lifecycle planning look like.

More everyday fixes from our helpdesk: how to recall an email in Outlook.