When a hard drive or SSD fills up beyond around 85 to 90 percent full, Windows can slow down noticeably, particularly for tasks that rely on temporary files or virtual memory. Rather than guessing where your space has gone, Windows has a built-in tool that breaks your drive down visually by category and folder size, making the biggest offenders easy to spot.
Key takeaway: Settings > System > Storage shows exactly which folders and file types are using the most space, letting you target the biggest space hogs first instead of deleting files at random.
Using the built-in Storage breakdown
- Open Settings > System > Storage.
- Wait a moment while Windows scans your drive and builds a breakdown by category (Apps, Documents, Temporary files, and so on).
- Click on the largest category to drill down further and see exactly what's inside it.
- Under "Apps & features," click the "Sort by" dropdown and choose Size, to instantly see your biggest installed programs.
Before you start: Never delete files you don't recognise from inside the Windows or Program Files folders directly — use the Storage tool's own categories and the guidance below instead of browsing system folders manually.
Finding large individual files
- Open File Explorer and click into your main drive (usually C:).
- Click the search box and type size:gigantic (or size:huge for slightly smaller results) — this is a built-in File Explorer search filter.
- Press Enter and let the search complete; this may take a few minutes on a large drive.
- Review the results, which will show every large file, often revealing forgotten video files, old ISO disc images, or oversized backups.
What's usually safe to delete
Old downloaded installer files (.exe, .msi) for software you've already installed, duplicate or outdated video files, old virtual machine disk files, and forgotten ISO images are common, safe targets. Always double-check a file isn't something you still need before deleting it.
Tip: Sort your Downloads folder by size (right-click an empty area, choose Sort by > Size) — it's one of the most common places for large forgotten installer files to accumulate over the years.
Checking cloud backup folders and virtual machine files
Two categories of large files are particularly easy to overlook because they don't show up prominently in everyday browsing. The first is old local backup files created by phone backup software or camera import tools, which can quietly accumulate full copies of a phone's photo library each time you connect it, even after the same photos have long since been copied elsewhere. The second is virtual machine disk files, often with a .vhd, .vhdx, or .vmdk extension, created by virtualisation software if you've ever set one up to test another operating system — these commonly reserve tens of gigabytes each, even for a virtual machine you only used once and forgot about.
Both types are safe to search for directly using File Explorer's search box: type the relevant file extension preceded by a dot, such as *.vhdx, into the search bar while your main drive is selected, and review what comes up before deciding what to remove.
Frequently asked questions
- How full does my drive need to be before it affects performance?
- Problems typically start becoming noticeable once a drive passes about 90 percent full, as Windows has less room to manage temporary files and virtual memory efficiently.
- Is it safe to delete files shown under "Temporary files" in Storage settings?
- Yes, this category is specifically curated by Windows to only include safe-to-remove temporary data, cache files, and old update leftovers.
- What's the difference between size:gigantic and size:huge in File Explorer search?
- They're preset size ranges built into Windows search — gigantic finds files over roughly 4GB, while huge covers a slightly lower range, useful if your gigantic search doesn't turn up much.