A system file is an important file which an operating system needs to be able to work properly. System files are found mainly in computers and device drivers. They can contain important information. They can contain information which enables a computer to start. They can also contain information which tells the computer how to run properly as you use it. Deleting a system file can damage a computer or make it unusable. System files in a Windows operating system are found in the System32 folder, the most important folder on the computer's hard drive. Most system files cannot be edited or deleted as they are always in use by the system.