When I try to open a program or a file it opens up a window with a lot of letters and symbols. The url includes notepad, example: rundll32.exe-notepad. On the top line it says, this program can’t run in DOS mode. I can’t restore my PC because it opens up to a window that I explained above. How do I fix this?
It sounds like the file association for .exe files has been changed. EXE files are executable files; they launch applications. For example, Winword.exe is the executable file that opens Microsoft Word. However, if the .exe file extension has been lost, Windows doesn’t know what to do when the executable is clicked or launched as part of normal startup. In this case, it sounds like Windows has been instructed to load the rundll32.exe file on startup and it thinks that Notepad is the appropriate choice for this exe file. Unfortunately, Notepad is the wrong choice and you are seeing a bunch of meaningless characters when Notepad opens.
Restoring the Exe File Extension in Windows XP
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Since System Restore requires the launching of an executable file, you are in a catch-22. You can’t restore your system because the .exe file association has been lost. Therefore, we can’t rely on rolling back the system to an earlier point and must address the issue directly. You will need to restore the .exe file extension manually. If you have Windows 98 or XP, this is pretty easy to do. You should be able to access My Computer from the Start menu. From there, click on Tools > Folder Options and select the File Types tab. Scroll through the list, in search of .exe.
The .exe extension may or may not be listed. If it is, edit the file association so that it reads “application.” If it is not listed, click the New button and type in “EXE” in the box labeled “File extension.” Under Associated File Type, select “application.” Click the Restore or OK button.
Restoring the Exe File Extension in Windows Vista
Restoring the .exe file extension in Windows Vista is not quite so easy. It involves editing the Windows registry which is extremely risky. According to FileExt.com, you can do this yourself by copying and pasting the following into Notepad and saving the file with a .reg extension:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.exe]
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.exe\OpenWithList]
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.exe\OpenWithProgids]
“exefile”=hex(0):
Once saved, close the document. Now, reopen it. Alternately, you can right click it and choose Merge. You will be prompted with a series of warnings. Confirm your choice and reboot your computer once the process is complete. Your computer’s .exe file association should be fixed.
Possible Virus Infection
How did this happen in the first place? Several computer viruses have been known to change the .exe file association including the notorious Sir Cam worm. Because of past computer virus issues having changed the .exe file extension, it’s in your best interest to run a complete system scan to ensure that your computer is clean. Update your computer security software first and then run a thorough scan of your entire system.
