Unable to Start a Program with an .exe File Extension

Symptom
When you try to launch an application (.exe files), the following error message appears and the program does not run.
Cause
This problem occurs if the .exe file association in the registry is corrupt. This behavior is generally caused by viruses; one of which is SirCam virus, which modifies the .exe file association in registry.
Resolution
Method 1: Fixing the association settings automatically
Download exefix_xp.com utility and save to Desktop. Double-click the file to run it. This utility fixes the exefile association in the registry automatically.
Additional tip: To run the utility silently (without any prompts), use the -silent parameter. Open a Command window (Command.com) and type:
C:\Utilities\exefix_xp.com -silent
Assuming that the exefix_xp.com is placed in the C:\Utilities directory.
Method 2: Fixing the association settings using Registry editor
Click Start, Run and type Command
Type the following commands one by one:
cd\windowsregedit
If Registry Editor opens successfully, then navigate to the following key:
HKEY_CLASSES_ROOT \ exefile \ shell \ open \ command
Double-click the (Default) value in the right pane
Delete the current value data, and then type:
"%1" %*(ie., quote-percent-one-quote-space-percent-asterisk.)
Navigate to:
HKEY_CLASSES_ROOT\.exe
In the right-pane, set (default) to exefile
Exit the Registry Editor.
If you're unable to launch Regedit.exe even from Command Prompt, try this:
copy regedit.exe regedit.comregedit.com