Files that contain the .003 file extension are split archive files. These files are created by archive and compression applications, such as the WinRar or WinZip programs. These software programs are used to take large files and collections of files and compress them into a single archive folder. The resulting archives can then be split into multiple volumes using software like HJSplit or SplitJoin.
When an archive file is split, each volume of the archive is assigned a numbered file suffix, usually in sequence. Files with the .003 extension are usually the third volume of the split file archive. Before you can open the .003 file, you will need to merge all of the archive volumes together.
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