What Are System Files on Windows? Here’s What You Need to Know

Windows has hundreds of thousands of files, but not all are created equal—some are more important than others. The OS has special types of files known as system files, and they play an important, and sometimes critical, role in helping Windows and its various components function properly. That’s why it’s a good idea to know what you can about them.

So what are system files on Windows, where can you find them, and how do you fix them when something goes wrong? Let’s find out.

What Are System Files on Windows?

System files are files that processes, apps, and device drivers on Windows need to operate properly. Without them, you’d notice, for example, that certain processes are generating errors, apps are crashing, and hardware isn’t working. In some scenarios, damaged or missing system files can lead to system shutdowns, restarts, or even crashes.

A popular example of a system file is kernel32.dll, and one of its main functions is memory management, meaning it ensures Windows, its processes, and apps have enough memory to operate. A corrupted kernel32.dll can cause all kinds of memory problems on your computer. For example, apps would try to occupy the same space in Random Access Memory (RAM), leading to errors or system crashes.

Furthermore, you should always let the OS make changes to system files, which it naturally does when you update the system, apps, and drivers, and install or uninstall things. Everything about system files, from their names to where they’re located on your storage drive, serves a purpose. You can interrupt it if you attempt to rename, move, or delete them.

The Different Types of System File Extensions on Windows

You’ll come across various types of system files on Windows. Here are nine examples of those files by extension type:

1. SYS: A file with the SYS extension is a Windows operating file. It contains information, such as settings and configurations, that Windows needs to operate correctly. These files are critical to the operation of Windows, which is why you’ll find that the OS hides them and places permissions to protect them from tampering.
2. DLL: A DLL (Dynamic Linked Library) is a file that contains a set of instructions and configurations that Windows programs use to perform tasks. Multiple Windows programs can access a single DLL at a time, reducing the need for them to place more information in physical memory or have extra lines of code.
3. CAB: A CAB file or Cabinet file is a compressed library of files, which includes other systems files and software and driver installation files. They’re Microsoft’s very own archived file type, and the data inside them is compressed using lossless compression.
4. MSI: An MSI (Microsoft System Installer) file is a file that contains a set of instructions that tell Windows Installer – the built-in program that handles the installation and uninstallation of programs – how to install a program.
5. ICO: An ICO (Icon File) is a file that’s made up of one or more images. Windows uses this file to graphically represent the executable of a program. So when you see the icon of a shortcut on your desktop, for instance, just know that its image is stored in an ICO file.
6. LNK: A file with the LNK extension indicates that it’s a Windows shortcut. This means that when you double-click it, you will gain quick access to a particular item on the computer, such as an app, file, or folder. These system file types are usually associated with desktop shortcuts.
7. DMP: A DMP file is known as a Windows Memory Dump file, and the OS creates them when an app experiences an error or a crash. By analyzing a DMP file, you can figure out what went wrong with a misbehaving program.
8. TMP: Windows programs use files with the TMP (Temporary File) extension to store temporary data during execution. These files are not really important and serve to improve an app’s performance. They’re usually deleted by the program once you close it.
9. INI: The INI file is a configuration file that contains instructions for Windows programs to execute.

Where Can I Find System Files on Windows?

Most of the system files on Windows are located on your local drive (C:), and you can find some of them in the root directory.

A well-known location for system files is the System32 (for 32-bit systems) or SysWOW64 (for 64-bit systems) folder. To find them, open File Explorer by pressing Win + E. Then, go to This PC > Local Disk (C:) > Windows > System32 or SysWOW64.

The System32 and SysWOW64 folders are known as System folders because of the many system files they contain.

How to Reveal Hidden System Files on Windows

Windows has hidden some system files by default to prevent you from accessing them. To unhide them, start by opening the Control Panel, heading to Appearance and Personalization, and clicking the Show hidden files and folders link.

This will open the View tab of the File Explorer Options dialog box. To reveal the system files, you’ll have to check the Show hidden files, folders, and drives radial button and uncheck the Hide protected operating system files check box.

Now, you’ll be able to see the system files.

How to Fix Missing or Corrupted System Files on Windows

Some changes made to your computer can lead to system files becoming deleted or corrupted. You can be responsible for these changes, or they can be the result of a malfunctioning app, process, or the dirty work of a virus. If you encounter any issues regarding system files, please read our guide on how to repair corrupted files on Windows using built-in tools.

System Files on Windows, Demystified

As you can see, system files are an important part of your Windows operating system. If you ever come across one, you should avoid tampering with it unless you’re absolutely sure you know what you’re doing and that they aren’t critical to the operation of Windows or any of its programs.

And should something go wrong with the system files on your Windows computer, it’s good to know there are ways to fix them.