What’s the safest way to find what’s filling up my C: drive?

Start with Windows Settings, then System, then Storage. It gives you a rough breakdown and offers cleanup for temporary files. Read the categories before selecting anything, especially Downloads, since that may contain files you still want.

A disk-usage viewer can make this much easier than poking through folders one by one. WizTree and WinDirStat are examples. Scan C: and look for unusually large folders or files, then check what they are before removing them. The viewer shows where space is used, but it can’t tell you whether a file is safe to delete.

With under a gigabyte left, first move or remove files you recognize, like old videos, installers, or games you no longer use. Empty the Recycle Bin too. If you need a quick bit of breathing room, Windows’ temporary-file cleanup is a safer starting point than deleting things directly from the Windows folder.

Be careful with advice to clear system folders such as SoftwareDistribution or random AppData folders. Some temporary files can be removed, but apps may be using them, and system folders can affect updates or Windows. Don’t delete a large item just because a scan makes it easy to spot. Check what it belongs to first.

Also check whether Windows itself is reporting a temporary-file or update cleanup option in Storage. Some Windows installations have more space tied up in update-related files than you’d expect, but the exact cause varies. If one enormous system file stands out, look up its purpose or ask for help before touching it.