Windows Inside & Out · Windows Under the Hood · Lesson 3 of 5

Where Windows Keeps Things

Find the main folders on drive C, and reveal hidden files and extensions.

Extensions and hidden items

Every file has a name, like Budget.xlsx. The part after the last dot is the file name extension. It tells Windows what kind of file it is and which app opens it.

• .pdf: a document for reading.
• .jpg or .png: a picture.
• .docx: a Word document.
• .exe: a program, something that runs and can make changes to your computer.

Windows hides extensions by default. That looks tidy, but scammers take advantage of it. They name a harmful program invoice.pdf.exe. With extensions hidden, you only see invoice.pdf, which looks like a harmless document. Only the last extension counts, so it's really a program.

Showing extensions is a smart safety step. In File Explorer, select View > Show > File name extensions.

Windows also hides some files and folders on purpose. Hidden items are files Windows keeps out of sight so they don't get moved or deleted by accident. To see them, select View > Show > Hidden items. They look a little faded.

Seeing hidden items is safe. Deleting or moving them is not, unless you know exactly what they are. You can turn the option back off at any time.

On a Mac, choose Finder > Settings > Advanced and turn on Show all filename extensions. In a Finder window, Command+Shift+. shows hidden files.

On the practice computer, turn on File name extensions and look closely at the invoice. Then turn on Hidden items and open C:\Users\You.

The main folders on drive C

Your computer's main storage is called drive C, written C:. Open File Explorer, select This PC, then Local Disk (C:). You'll see a few big folders.

• Windows: Windows' own system files. Leave this one alone. Deleting things here can stop the computer from starting.
• Program Files: where most apps are installed. Program Files (x86) holds 32-bit apps. 32-bit is an older style of app that still runs on today's computers.
• Users: one folder for each person who signs in to this computer.

A path is the full address of a file or folder, with each folder separated by a backslash (\). Your own folder's path is C:\Users\ followed by your account name.

Inside your folder are Desktop, Documents, Downloads, Pictures, Music and Videos. This is where your own stuff lives, and what you should back up.

With hidden items on, you'll also see AppData. It holds settings and saved data for your apps, like your browser's profile. Apps manage it themselves. Inside are folders such as Local, for things that stay on this computer, and Roaming, for settings that can follow you between computers on some work networks.

Some fixes say to clear a folder in AppData, often a cache, a store of temporary copies that helps an app load faster. Only do this when a trusted guide names the exact folder, and close the app first.

A quick tip: type %appdata% in File Explorer's address bar and press Enter to jump straight to the Roaming folder.

On a Mac, apps live in the Applications folder, and your files are in your home folder, inside Users.