//[Last update 2003-05-17]
program DelSelf;
uses
  Windows;

procedure DeleteSelf;
{$DEFINE XPVERSIONCHECK}
{
  This code is only compatible with Windows 95, 98, Me and NT 4, 2000!
  No XP support, yet. If I find out how this could work, I'll update the code.
  If your code will definitely not run on XP, you may undefine the compiler
  variable XPVERSIONCHECK which will strip the version checking off the code :)

  Note, this version will only work, as long as the functions are imported through
  the import table. This is true for any Win32 app and Kernel32.dll!
  Anyway, if you introduce symbol names, that conflict with the function names,
  this code is likely to break! I am not sure wether this is possible at all for
  kernel32 functions, because kernel32.dll is implicitly bound, but maybe it is ...
  so be warned!

  Also, this code is only compatible with the i386 processor architecture. This
  becomes evident as soon as you recognise the assembler parts in the code.

  This code is PUBLIC DOMAIN!!!
}
var
  szModuleName: array[0..MAX_PATH - 1] of Char;
  pExitProcess,
    pDeleteFile,
    pFreeLibrary,
    pUnmapViewOfFile: Pointer;
  hModule: THandle;
{$IFDEF XPVERSIONCHECK}
  osvi:TOSVersionInfo;
{$ENDIF XPVERSIONCHECK}
asm
{$IFDEF XPVERSIONCHECK}
// Check for version and exit if XP detected
    lea  eax, osvi
    push eax
// Set size member
    mov  osvi.dwOSVersionInfoSize, $94
    call GetVersionEx
    test eax, eax
    jz   @@ExitThis // Version could not be determined!
// Check for version 5 (2000, XP)
    cmp  osvi.dwMajorVersion, 5
    jl   @@startthrough
// Check for minor version greater or equal 1 (means XP or higher)
    cmp  osvi.dwMinorVersion, 1
    jl   @@startthrough
// else Exit
@@ExitThis:
    call ExitProc
@@startthrough:
    mov  eax, osvi.dwPlatformId
    mov  hModule, 0
    cmp  eax, VER_PLATFORM_WIN32_NT
    je   @@foo1
    mov  hModule, $80000000 // 9x, Me
@@foo1:
    push hModule
{$ELSE XPVERSIONCHECK}
    call GetVersion
    push eax
{$ENDIF XPVERSIONCHECK}
(*** Get real address of ExitProcess ***)
{ Dereference the function addresses from the jump table:
  I'll briefly explain on this first function ('ExitProcess')
  Load effective address. EAX points to code like FF 25 XX XX XX XX -> jmp ds:XXXXXXXX }
    lea eax, [ExitProcess]
{ Ignore the jump instruction of 2 bytes size (i.e. FF 25) }
    mov eax, [eax+2]
{ EAX holds now the XX XX XX XX from above metacode, i.e. a pointer to the 'real' address }
    mov  eax, [eax]
{ EAX now holds the 'real' address of the function ExitProcess within our realm }
    mov  pExitProcess, eax
{ The following code works accordingly ...}
(*** Get real address of DeleteFileA ***)
    lea eax, [DeleteFileA]
    mov eax, [eax+2]
    mov  eax, [eax]
    mov  pDeleteFile, eax
(*** Get real address of FreeLibrary ***)
    lea eax, [FreeLibrary]
    mov eax, [eax+2]
    mov  eax, [eax]
    mov  pFreeLibrary, eax
(*** Get real address of UnmapViewOfFile ***)
    lea eax, [UnmapViewOfFile]
    mov eax, [eax+2]
    mov  eax, [eax]
    mov  pUnmapViewOfFile, eax
(*** Now the "main code" ***)
    push 0
    call GetModuleHandleA
    mov hModule, eax
(*** Got module handle of this instance ***)
    push MAX_PATH
    lea eax, szModuleName
    push eax
    push hModule
    call GetModuleFileNameA
(*** szModuleName now holds the file name of our instance's module ***)
(*** Checking for Windows 9x / Windows NT platform ***)
    pop  eax
    test eax, $80000000
    jz @@NTplatform
//@@9xplatform: // Windows 95, 98, Me
    lea eax, szModuleName
    push System.ExitCode
    push 0
    push eax
    push pExitProcess
    push hModule
    push pDeleteFile
    push pFreeLibrary
    ret
@@NTplatform: // Windows NT, 2000
    push 4
    call CloseHandle;
    lea eax, szModuleName
    push System.ExitCode
    push 0
    push eax
    push pExitProcess
    push hModule
    push pDeleteFile
    push pUnmapViewOfFile
    ret
{$IFDEF XPVERSIONCHECK}{$UNDEF XPVERSIONCHECK}{$ENDIF}
end;

begin
  DeleteSelf;
end.

{
Looking at the older code (without XP version check) from a disassembler ;)

DeleteSelf      proc near

szModuleName    = byte ptr -118h
hModule         = dword ptr -14h
pUnmapViewOfFile= dword ptr -10h
pFreeLibrary    = dword ptr -0Ch
pDeleteFile     = dword ptr -8
pExitProcess    = dword ptr -4
                push    ebp
                mov     ebp, esp
                add     esp, -118h
                lea     eax, ExitProcess_JumpEntry
                mov     eax, [eax+2]
                mov     eax, [eax]
                mov     [ebp+pExitProcess], eax
                lea     eax, DeleteFile_JumpEntry
                mov     eax, [eax+2]
                mov     eax, [eax]
                mov     [ebp+pDeleteFile], eax
                lea     eax, FreeLibrary_JumpEntry
                mov     eax, [eax+2]
                mov     eax, [eax]
                mov     [ebp+pFreeLibrary], eax
                lea     eax, UnmapViewOfFile_JumpEntry
                mov     eax, [eax+2]
                mov     eax, [eax]
                mov     [ebp+pUnmapViewOfFile], eax
                push    0
                call    GetModuleHandleA_0
                mov     [ebp+hModule], eax
                push    260
                lea     eax, [ebp+szModuleName]
                push    eax
                push    [ebp+hModule]
                call    GetModuleFileNameA_1
                call    GetVersion
                test    eax, 80000000h
                jz      short NTplatform
                lea     eax, [ebp+szModuleName]
                push    ds:system_Exitcode
                push    0
                push    eax
                push    [ebp+pExitProcess]
                push    [ebp+hModule]
                push    [ebp+pDeleteFile]
                push    [ebp+pFreeLibrary]
                retn
NTplatform:
                push    4
                call    CloseHandle_0
                lea     eax, [ebp+szModuleName]
                push    ds:system_Exitcode
                push    0
                push    eax
                push    [ebp+pExitProcess]
                push    [ebp+hModule]
                push    [ebp+pDeleteFile]
                push    [ebp+pUnmapViewOfFile]
                retn
DeleteSelf      endp
}