[dec]

Hola,

Primero que nada (aunque parezca simple) comprueba que existe el archivo en cuestión. Por otro lado comprueba el resultado de la función "ShellExecute", y llegado el caso comprueba también el último error con la función "GetLastError()".

Código Delphi [-]

if ShellExecute({parámetros}) <= 32 then
begin
  ShowMessage( SysErrorMessage( GetLastError() ) );
end;

Edito: Tal vez me pasé de listo. Mirando la ayuda no veo referencia a que pueda usarse "GetLastError()"... y sí a que la función puede retornar un entero menor o igual que 32 en caso de éxito, o uno de los siguientes enteros/constantes en caso de error:

0 The operating system is out of memory or resources. 
ERROR_FILE_NOT_FOUND The specified file was not found. 
ERROR_PATH_NOT_FOUND The specified path was not found. 
ERROR_BAD_FORMAT The .exe file is invalid (non-Microsoft Win32 .exe or error in .exe image). 
SE_ERR_ACCESSDENIED The operating system denied access to the specified file. 
SE_ERR_ASSOCINCOMPLETE The file name association is incomplete or invalid. 
SE_ERR_DDEBUSY The Dynamic Data Exchange (DDE) transaction could not be completed because other DDE transactions were being processed. 
SE_ERR_DDEFAIL The DDE transaction failed. 
SE_ERR_DDETIMEOUT The DDE transaction could not be completed because the request timed out. 
SE_ERR_DLLNOTFOUND The specified DLL was not found. 
SE_ERR_FNF The specified file was not found. 
SE_ERR_NOASSOC There is no application associated with the given file name extension. This error will also be returned if you attempt to print a file that is not printable. 
SE_ERR_OOM There was not enough memory to complete the operation. 
SE_ERR_PNF The specified path was not found. 
SE_ERR_SHARE A sharing violation occurred.