problem: When you try to open EXE files, you may get errors messages like: "Access Denied", "Runtime error", or you may be asked what program you wish you open this file with.

 This is usually a symptom of a past virus or spyware infection.

solution:

1. Click Start, and then click Run.  


2. Type "command.com" , and then press Enter. (A DOS window opens.)
 

3. Type the following:
 
         "cd\\"

         "cd \\windows"
 
    Press Enter after typing each one.
 
4. Type copy "regedit.exe regedit.com" and then press Enter.
 
5. Type "start regedit.com" and then press Enter.
 
6. Navigate to and select the key:
 
    HKEY_CLASSES_ROOT\\exefile\\shell\\open\\command
 
7. In the right pane, double-click the (Default) value.
 
8. Delete the current value data, and then type:
 
     "%1" %*
 
 Tip: Type the characters: quote-percent-one-quote-space-percent-asterisk.
 
9. Close Regedit utility.

 

 

Source: http://support.microsoft.com/kb/555067