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What Could Be Causing The File Save Error Message

When you save changes in PE Explorer, you may get the following error message:

Can't create new image file, the original file has been probably packed.

The term "image file" is usually used instead of "executable file", because the latter sometimes is taken to mean only an .EXE file. An image file can be thought of as a "memory image" or "mirror image".

In most cases modifying resources does not affect the normal operation of the file, but occaisionally some modified files may become invalid after they have been changed.

There is a good chance the original executable file was compressed to have it protected from unauthorised modification by other users. Since PE Explorer detects and automatically unpacks only files compressed with UPX, Upack and NsPack, you have to go through the trouble of manually unpacking this compressed executable file before you can save your changes.

This is not viewed as a bug. We are not going to defeat the security attempts of other software authors. And we cannot support decompressing few hundred packers and protectors available on public.


1. Always create a backup copy of the original files before modifying! The PE structure is documented in detail, but the interaction of the various components is very extensive making it very difficult to reveal all the interactions within the file. Moreover, the original programmer may have implemented mechanisms to verify the integrity of the file against modifications. There IS a point to this, for instance that is safety from viruses.

2. Do not attempt to manipulate the section headers after modifying resources! It is very likely that the newly created file will appear to be invalid.

If modifications are required, the following procedure is recommended:

  • Review and analyze all structures and data in the file.
  • Make changes to section headers. "If in doubt don't change" is a good rule of thumb.
  • Create the new image and test it carefully.
  • Modify its resources.
  • Test it over and over again.


PE Explorer lets you save the modified file with the same extension as the original file has. However, you have an option to create a backup copy of the target file (enabled by default). So by no means you can overwrite any important files.

The newly created file will be saved either in the same folder where the original file is located, or in the Project folder if it was set. To set the default Project folder, click Tools > Customize and select a desired Project folder location. In this case, a backup copy of the target file will also be created in the Project folder.


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