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What is the .OLD File Extension?

.OLD File Extension Description:

The OLD file extension identifies old or archive files used by some operating systems and many applications. Files with the .old file extension can be created automatically by the software or manually by the user.

MS Windows typically uses the OLD file extension as a generic file extension to rename MSDOS system files such as the autoexec.bat and config.sys. The autoexec.bat system file is a plain-text batch file found in the boot device's root directory, and it automatically executes commands during system startup. The config.sys system file is also a text file containing special commands to configure the computer's hardware components so MS DOS and other applications can use these commands.

These 2 MS DOS system files are unnecessary in newer operating systems such as Windows. These files are renamed using the OLD file extension, so the files becomes autoexec.old and config.old. This prevents them from running during boot time, which speeds up both system startup and operation.

However, it is possible for the files to hold some old DOS-level drivers needed by the system, particularly by older OS versions. If problems occur, any of these system files with the OLD file extension can be copied to restore the files and correct the issues.

The OLD file extension also indicates or denotes a backup copy of a file. It normally represents an earlier version of a file. Files with the OLD file extension is sometimes used in order to have the initial file extension replaced.

It can also be appended to the filename as an additional type of file extension when a newer version of the file has been created or saved by a certain program. It is often placed after the original file extension. For instance, the document.xls.old means it is a backup copy of the file document.xls.

Multiple files with the same extension can be renamed to files with the OLD extension without the aid of an external program. An example of this is a group of files with the .txt extension being renamed to files with the .old file extension by typing ren *.txt *.old at the Command Prompt.

Author: Microsoft Corporation
Author URL:
Related Applications: Microsoft Windows
Common Path: C:/


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Do you have errors with .OLD files?

The Cause for .OLD files Errors:

When you encounter errors with .OLD files you are in all likelihood experiencing a serious Windows file error - this error might be the effect of damage to your program registry and action is needed to repair it immediately to avoid further damage to the operating system. Risks include device failure, blue screen errors and fatal crashes.

Symptoms of .OLD files Errors:

.OLD files error symptoms include program crashes, shut down or start up problems, slow system performance, laggy behaviour, screen freezing, beeping sounds, trouble opening application files as well as errors while installing software.

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