Fixing a corrupted file. Imposible?

In most cases it is almost impossible. Especially for .exe files which was corrupted.
However the following article describes the common methods;

Readily Available Solutions

1

Restore the lost file from a recent backup. Many programs create backups automatically. Microsoft Word, for example, backs up ".doc" files as ".wbk" files under the same folder. In this case, rename the ".wbk" file as ".doc" to open it.
2

Use the Windows Disk Utility. If you run Windows 98 or Millennium, click Start, Programs, Accessories, System Tools and Scan Disk. Select the appropriate drive. Click Thorough Check, Automatically Fix Errors and then press Start. If you run Windows 2000 or XP, open My Computer and right-click on the drive. Select Properties and then Tools. Check the "Now" option. Check both available options and click Start.
3

Utilize the System Restore tool after an installation or accidental disk format. A feature of Windows XP and Millennium, it rolls system files back to an earlier state when everything worked. Software installations, updates or removals sometimes make unwanted changes to the system.
Outside Sources
1

Use Partition Recovery or HDD Regenerator to recover or fix lost top-level folders that contain many file types. You can also utilize FAT Recovery or NTFS Recovery, if you are not certain of your file type.
2

Choose one of the following special-purpose recovery software. Each addresses a certain file type:

DOC Regenerator for Microsoft Word documents

XLS Regenerator for Microsoft Excel Files

Outlook Express Repair for emails from Outlook Express

Flash Recovery for image files

Music Recovery for audio files such as MP3, WMA and RA

CD & Recovery for files burned on one of those mediums

Partition Recovery or FAT Recovery for fixing corrupted files in removable memory such as flash drive, memory stick or pen memory having a FAT or FAT32 format
3

Hire a data recovery expert to match data fragments of corrupt files to fix data that software can't piece together. This should be the last resort after all attempts with software like those recommended above have failed. As the cost of hiring data recovery experts is very high, this measure is appropriate when the data is completely irreplaceable and its value is very high.