There are several factor which caused this.

  1. Virus infection
  2. Some software changed your settings
  3. You accidentally changed without noticing it

If when you double click on EXE and LNK files, nothing happened then this fix is what you’ve been looking for.
Or, when you right click on those files, you can’t find Open or something similar.

To fix this, it is easy. Just follow the steps.

  1. Open notepad. Copy everything below and paste it inside.

    [Version]
    Signature=”$Chicago$”

    [DefaultInstall]
    AddReg=RepairReg

    [RepairReg]
    HKLM,software\classes\exefile\shell\open\command,,0,”"”%1″” %*”
    HKLM,software\classes\batfile\shell\open\command,,0,”"”%1″” %*”
    HKLM,software\classes\comfile\shell\open\command,,0,”"”%1″” %*”
    HKLM,software\classes\piffile\shell\open\command,,0,”"”%1″” %*”
    HKLM,software\classes\scrfile\shell\open\command,,0,”"”%1″” /S”
    HKLM,software\classes\regfile\shell\open\command,,0,”regedit.exe “”%1″”"
    HKCU,software\Microsoft\Windows\CurrentVersion\Policies\System,DisableRegistryTools,0×10001,0×0000

  2. Click on save as, choose All files as save as type and name it as regfix.inf. Be sure that it is .inf.
  3. Then go to that file and right click it and click Install.
  4. It should be working now.

P/S: I got this regfix in a forum post. I forgot which forum. Sorry that I can’t credit the original author.