Andy’s PC has less storage space on an almost daily basis and he would like to get some of it back …

I frequently use the Disk Cleanup facility in Windows 10, but the amount of disk space taken up increases almost on a daily basis. Despite upgrading to Windows 10, Disk Cleanup still refers to disk space on Windows8_OS[C]. Is this the problem? Also, 3GB is Temporary Internet files, but deleting Temporary Files in Storage makes little or no difference. Andy

Before we start, I must remind you that you are totally responsible for your own PC and all your personal data. If you are going to run programs that delete files, or worse, you must have everything securely backed up first. Windows 10 includes a backup program that can back up your hard drive and also take a disk image. It’s also a good idea to create recovery media and to make separate copies of irreplaceable data files and family photos.

Now, disks usually take a few years to fill up, and the process should be too gradual to notice. When it isn’t, it rings alarm bells that suggest something bad is happening.

The most likely “bad thing” is that your PC has a malware infection. Run a spot check with a different anti-virus product such as Malwarebytes, Kaspersky or Hitman Pro, as mentioned in a recent answer. If they don’t find anything, restart your PC in safe mode with networking and run them again.

There are other possibilities, such as a runaway media cache, a PC that is creating too many system restore points, or an overgrown Windows search index file (windows.edb). Also, your file system may have been corrupted so it is showing incorrect values. To fix this, run a command prompt as administrator, type in chkdsk C: /f /v /x and schedule a reboot.

Either way, Windows8_OS[C] is not the problem. PC manufacturers can call the C: drive whatever they like, so I assume your machine shipped with a Windows8_OS[C] drive. Windows 10 doesn’t change the name when you do an in-place upgrade, so it would have stayed the same. You can change it, if you really want to.

Spring cleaning

Windows includes Disk Cleanup and other facilities for reclaiming hard drive space. However, Piriform’s free CCleaner (originally, Crap Cleaner) is the quickest and simplest way to delete temporary internet files, old log files and other accumulated junk. Download it from the original source as there are scammers who charge for it.

CCleaner can delete information you want. This includes your browser history, and website details stored in cookies on your hard drive. Before you run it, make sure you know the log-on details and passwords for all your websites, and save the current tabs in all your browsers.

For the best results, reboot your PC and run it before starting any programs that may object to CCleaner deleting their data.

CCleaner’s Tools section includes utilities to analyse your hard drive and to find duplicate files. However, neither is particularly good, so use separate programs instead.

Duplicate file finders

You may already have a duplicate file finder. If not, there are lots to choose from, so try two or three to find one you like. In general, I prefer de-dupers that let you choose one or two directories to compare. That cuts down the number of comparisons, which speeds up the process. It also makes it easy to avoid back-up and system directories.

NirSoft’s SearchMyFiles is a good basic duplicate file finder. You can tell it to stop searching after finding a specific number of duplicates, such as 100, which avoids getting overwhelmed.

For as long as I can remember, I’ve used Big Bang Enterprises’ DoubleKiller on my home PCs. It doesn’t have the simplest user interface but it’s fast, flexible, and does the job.

If you have a lot of photos and music files, you could also try Anti-Twin, which I mentioned in 2011. Anti-Twin has a “compare file content” option that compares the binary content of various files. It can therefore find dupes that are not identical but very similar, such as different files of the same music track. De-dupers that work on file sizes and CRC or MD5 checks won’t find those. Duplicate Cleaner has similar features.

Tracking disk space

If you are running short of hard drive space, it helps to know what’s using it. Disk analysers tell you. Most also provide some sort of visualisation, such as a pie chart or tree-map.

As with de-dupers, there are dozens of disk analysers, and most people try a few until they find one they like.

Facebook Twitter Pinterest ‘You may need to make space by moving some large files to an external hard drive.’ Photograph: Jeffrey Hamilton/Getty Images

If you don’t already have one, Windows Directory Statistics (WinDirStat) is a popular choice. It lists directories in size order, and you can drill down to find out which folders and then files take up the most space. It also lists the main types of file, so you can see how much space is consumed by MP4 video files, MP3 music files, jpg images. dll files and so on.

Freeware alternatives include SpaceSniffer and TreeSize Free. There are paid-for programs that will track disk space over time, such as FolderSizes. I don’t know of a simple free program that does this, but geeks can do it by scripting Windows’ built-in Performance Monitor (PerfMon).

You may need to make space by moving some large files to an external hard drive or burning them to DVD etc.

Check your drive

We are about to tread some dangerous ground, and people of a nervous disposition may want to watch cat videos on YouTube instead. Or download Macrium Reflect Free and back up their hard-drive partitions …

Press WinKey-X to bring up the super space-cadet menu and either hit k or click Disk Management. This will show you the layout of your hard drive. There should be a Disk 0 recovery partition, installed by the PC manufacturer, plus one or more recovery partitions installed by Windows. Messing around with them may well stop your PC from working.

Your PC probably has a separate partition for WinRE, the Windows Recovery Environment. (For more details, see last week’s answer, How can I fix my PC when Windows 10 won’t boot?) In Windows 8, WinRE fitted comfortably into a 300MB reserved partition. However, when you upgraded, the new WinRE wouldn’t fit, so Windows 10 probably created a separate 450MB or 500MB partition at the end of the C: drive.

All these partitions are too small to bother about. However, Windows 8 also included a copy of the original operating system so that you could reset your PC to factory condition. That would take up at least 5GB, and the manufacturer might reasonably have put it on an 8GB partition. If you find one of those, the space might be worth recovering, but doing it with a partition management program is tedious and somewhat hazardous. (Just deleting the partition creates “unallocated space”: it’s not usable unless you can merge that space into your C: drive.)

Given that your current Windows 10 installation needs a clean-up, it might be simpler to download Windows 10 to an empty 8GB thumb drive and do a clean installation. This will delete all your existing programs and data, so you really must have everything backed up.

Have you got another question for Jack? Email it to Ask.Jack@theguardian.com

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