HINSTANCE i = ShellExecute(Handle, "open", "PROGRAM", 0, 0, SW_SHOWNORMAL);
if((int)i < 33)
  ShowMessage("PROGRAM을 실행할 수 없습니다.");

여기서 i 값을 보면 결과를 알 수 있습니다.

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-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 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 dynamic-link library 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.
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.

스머프 님이 쓰신 글 :
: 안녕하세요..
:
: 궁금한 점이 있어서 질문드립니다.
:
:
: ShellExecute( Application.Handle, 'open', 'exam',pPath, 'C:\', W_SHOWNORMAL );
:
: 라인으로 exam.exe 라는 외부 프로그램을 실행시키는데
:
: 이 프로그램(exam.exe)이 실행을 성공적으로 마치면 리턴값이 '0' 이 날라오고
:
: 중간에 오류가 나면 다른 숫자가 날라옵니다..
:
: 이 리턴값을 알 수 있는 방법이 없나요..??
:
: 답변좀 부탁드리겠습니다....
:
:
:
: