C drive is full. How can I extend C drive without losing data on Windows 10 PC?

C drive full? First things first, let's hit up the built-in Disk Cleanup tool. This bad boy can sift through your system and find a ton of stuff you can safely toss:

• Open Disk Cleanup: Just search for “Disk Cleanup” in the Start menu. Select your C drive when prompted.
• Choose What to Clean: It’ll scan and give you a checklist. You’ll see stuff like “Temporary Files,” “Recycle Bin,” and “Thumbnails.” Check the boxes for what you want to delete. If you see “Windows Update Cleanup” in there, that can reclaim a good chunk of space too.
• Run It: Press “OK,” and it’ll do its thing.