Why is my Windows 11 PC so slow?

"It was fine when we bought it." That's how nearly every slow-PC conversation starts. Then it got slow in the spring, everyone learned to make a cup of tea while it booted, and two years later it takes four minutes to open a Word document and nobody can remember it being any different.

Slow Windows PCs are the second thing on my home tech support page, after Wi-Fi. Most of them don't need a reinstall, and quite a few don't need me. Here's what I check, in order.

Open Task Manager before you change anything

Press Ctrl, Shift and Esc together. Task Manager opens. Click Performance on the left and leave it open while you do whatever is slow: open the browser, start Outlook, load the photo you were trying to print.

You're looking at three graphs. CPU, Memory and Disk. One of them will usually sit near 100% while the machine crawls, and that one tells you which of the fixes below matters. Everything else is guessing. Buying more memory for a laptop whose real problem is the hard drive is a very tidy way to spend money on nothing.

Disk at 100%

This is the most common one on cheaper and older laptops, and the most satisfying to fix. Click the Disk graph and look at the type. If it says HDD, the PC is running Windows 11 off a spinning hard drive, and Windows 11 on a spinning drive is miserable no matter what else you do. Updates, the antivirus scan and the search index all queue up for the same slow disk, and you wait behind them.

The fix is to swap it for a solid-state drive and copy everything across. On most laptops that's a screwdriver job, and it's the single change that makes an old machine feel new. It's the first thing I'd look at before anyone talks about replacing the whole PC.

If the disk is already an SSD and it still sits at 100%, it's usually something running in the background. The Processes tab, sorted by Disk, tells you what.

Memory nearly full

Microsoft's minimum requirement for Windows 11 is 4 GB of memory. That's the minimum to install it. It isn't enough to run a modern browser with a few tabs, a Teams call and a printer driver at the same time, and on a 4 GB laptop the memory graph is pinned at 90% before you've opened anything. Windows then shuffles memory to the disk to cope, which is why a full memory graph often looks like a disk problem too.

My view, for a home PC in 2026: 8 GB is the floor, and 16 GB is comfortable. Some laptops can take more memory. Many recent thin ones have it soldered to the board and can't, which is worth knowing before you buy one.

The things you can do yourself

Microsoft keeps a list of tips to improve PC performance, and the useful ones, in the order I'd try them, are these.

• Startup apps. In Task Manager, click Startup apps. Everything with a high "Startup impact" that you don't need the moment the PC turns on (game launchers, printer utilities, the music app from 2021) can be set to Disabled. It still works when you open it.
• Free space. Settings, System, Storage. If the drive is nearly full, run Storage Sense and clear temporary files. A drive with under a tenth of its space left gets noticeably slower.
• Updates. Settings, Windows Update, then Check for updates, and look under Advanced options at Optional updates for driver fixes.
• A virus scan. Windows Security, Virus & threat protection, Quick scan.
• Restart it properly. Start, Power, Restart. Not shut down and power on, which on many laptops is closer to waking from sleep.

One timing note. Microsoft releases its monthly security updates on the second Tuesday of the month, and for the first hour or so after a big one installs, a PC can be slow while it finishes the job and rebuilds its search index. If the slowness is always on a Wednesday, that's probably all it is.

What not to download

Don't install a "PC cleaner" or "registry optimiser" you found through an advert. Most of them do nothing useful, some nag you to pay for a licence to fix problems they invented, and a few are worse than that. Microsoft has its own free one, PC Manager, linked from the same support page, if you really want an app for it. The steps above do the same job.

And be wary of anyone whose first move is to wipe the machine. Windows has a "Reset this PC" option that can keep your files. Occasionally it's the right answer. It's rarely the first one.

When it isn't worth fixing

Microsoft's own page says older PCs with outdated hardware may not improve much, and that's true. A laptop with 4 GB of soldered memory and a slow processor will stay slow however tidy you make it. I'll tell you that early rather than charge you for poking at it. The decision then is simple: if the case, screen and battery are fine and it only needs an SSD, fix it. If it needs everything, put the money towards a new one.

What I do when I come out

Same order as above, but with the tools to finish it: the Task Manager check, a drive health test, the SSD swap with your files moved across if it needs one, startup tidied, updates and drivers brought up to date, and a straight answer if it's due a replacement. There's no price list, because a full startup folder and a dying hard drive are different jobs. Describe what it's doing and I'll tell you what I'd do and what it will cost before I touch anything. I come out in London, or work remotely for anywhere else in the UK.

If you'd rather it never got this slow again, the home device security plan is £10 a month per device: updates kept current, the machine kept locked down and checked, and up to five problems fixed each month.

Common questions

Will more RAM speed up my laptop?

Only if memory is what's full. Check the Memory graph in Task Manager while it's slow. If it's near the top, more RAM helps, provided your laptop can take it. If the disk graph is the one at 100%, an SSD will do far more.

Is it worth putting an SSD in an old laptop?

Usually, yes. If it's still on a spinning hard drive, an SSD is the biggest single speed-up you can buy. It's not worth it if the laptop has other faults, like a failing battery or a cracked screen.

Do I need to reinstall Windows to fix a slow PC?

Rarely. Most slow PCs are a full drive, too many startup apps, too little memory or a hard drive. Reset this PC, keeping your files, is there for the cases that are left.