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Help Saved file is always corrupted

Posted: 14 Feb 2009 23:53
by rktkt
I hope you can help this lady who knows nothing about hex editing.

I am using HxD which seems very easy to use for me to change a few words of text in an exe file. However, if I only change just one text character (have tried deleting old letter and also overtyping), then when I save and run the new exe it gives the error 'This self-extracting executatble file has been corrupted. The instalation has been terminated'.
If I change nothing and save the file, it runs OK.

What an I doing wrong?

Ruth

Re: Help Saved file is always corrupted

Posted: 15 Feb 2009 17:06
by Maël
Hello Ruth,

The executable you are trying to modify is compressed and if you change a part of the compressed executable you corrupt it.
If the text you change is only displayed, its exact content would not be important (for the program). But since the file is compressed, this text is interpreted (i.e. decoded/decompressed) and a such must represent a valid sequence. It is very unlikely or difficult to change the text such that it stays valid for the decompression algorithm.

Another reason could be that the program has a checksum. If the contents doesn't match the checksum the program quits with an error. Checksums can be stored in different places in the file, it entirely depends on the author of the program.

Hope this helps,
Maël

Re: Help Saved file is always corrupted

Posted: 15 Feb 2009 21:53
by rktkt
Hello Maël,

Thank you for taking the time to answer my question.

Ruth