Running Out of Disk Space on Windows: How to Find What Is Using It and Free It Up

A hard drive that is almost full is not just inconvenient — it actively slows your PC down, can prevent Windows updates from installing, and in severe cases will cause applications to crash when they cannot write temporary files. The good news is that most machines have significant recoverable space that is easy to free up without deleting anything you actually need.

Step 1: Find Out What Is Actually Using the Space

Before deleting anything, understand where the space is going. The free tool WinDirStat (Windows Directory Statistics) scans your drive and produces a visual map showing which folders and file types are consuming the most space. This takes the guesswork out of disk cleanup and often reveals surprises — a single folder of forgotten large video files, a bloated database, or log files that have grown unchecked for months.

Windows also has a built-in breakdown: go to Settings → System → Storage. Click on your drive to see a category breakdown (Apps, Temporary Files, Other, etc.) and drill into each category to understand what is there.

Step 2: Run Disk Cleanup and Remove Windows Update Files

Windows Disk Cleanup removes temporary files, cached web content, old error reports, and the previous Windows installation files that accumulate after major updates. Search for Disk Cleanup in the Start menu, select your C: drive, and click Clean up system files (the elevated version, which includes Windows Update cleanup). Tick everything offered, paying particular attention to:

• Windows Update Cleanup — often 5–15 GB on machines that have not been cleaned recently
• Previous Windows installation(s) — the Windows.old folder kept after a major version upgrade, which can be 20 GB or more
• Temporary files and Temporary internet files

Step 3: Enable Storage Sense

Storage Sense is Windows’ built-in automatic cleanup feature that runs in the background and removes temporary files, empties the Recycle Bin after a set number of days, and cleans up locally cached cloud files that have already been synced to OneDrive. Go to Settings → System → Storage → Storage Sense and turn it on. Configure it to run automatically when disk space is low, or on a weekly schedule. This prevents gradual accumulation from becoming a crisis.

Step 4: Uninstall Unused Applications

Go to Settings → Apps → Installed Apps and sort by Size. Work through the list and uninstall anything that is no longer used. Pay attention to large items that may have been installed by previous staff members or for a one-off project and never removed. Game launchers, old versions of software, trial applications, and manufacturer bloatware on new machines are all common space hogs.

Step 5: Move or Archive Large Files

Using WinDirStat from Step 1, identify any folders of large files that are rarely accessed — archived projects, old backups, large media files, or databases from discontinued applications. Move these to:

• An external hard drive or NAS for local archival
• OneDrive or SharePoint with Files On-Demand enabled, which keeps the files accessible via their original path but only downloads them locally when opened, freeing the local disk space
• A cloud archive tier (such as Azure Blob Cool or Cold storage) for large volumes of rarely accessed data at minimal cost

Step 6: Clear Application Caches and Log Files

Several applications build up large caches or log files over time that are safe to clear:

• Browser caches: In Chrome, Edge, or Firefox, go to Settings → Privacy → Clear browsing data and clear cached images and files. Browser caches of 10–20 GB are not unusual on machines that have never been cleared.
• Windows temp folder: Press Windows + R, type %temp%, and delete everything in the folder that opens (skip anything that is in use — Windows will tell you).
• Application logs: Check C:\inetpub\logs (IIS logs) and C:\Windows\Logs on server machines. On developer workstations, check for Docker images, npm caches, and IDE caches which can run into tens of gigabytes.

Step 7: Consider Upgrading the Drive

If your C: drive is a 128 GB or 256 GB SSD that came with the machine, it may simply be undersized for current workloads. Upgrading to a larger SSD — 512 GB or 1 TB — is relatively inexpensive and can be done without reinstalling Windows using disk cloning software such as Macrium Reflect or the migration tools provided by drive manufacturers like Samsung and Crucial.

Through our partnership with TechNest-Global, BIT Tech can source replacement drives and carry out the upgrade and migration for you. Get in touch if your team’s machines are running low on storage and you would like help assessing and resolving the problem.