Private Const MAX_PATH = 260
Private Const TH32CS_SNAPPROCESS = 2&

Private Type PROCESSENTRY32
   lSize As Long
   lUsage As Long
   lProcessId As Long
   lDefaultHeapId As Long
   lModuleId As Long
   lThreads As Long
   lParentProcessId As Long
   lPriClassBase As Long
   lFlags As Long
   sExeFile As String * MAX_PATH
End Type

Private Declare Function CreateToolhelpSnapshot Lib "kernel32" Alias "CreateToolhelp32Snapshot" (ByVal lFlags As Long, ByVal lProcessId As Long) As Long
Private Declare Function ProcessFirst Lib "kernel32" Alias "Process32First" (ByVal hSnapshot As Long, uProcess As PROCESSENTRY32) As Long
Private Declare Function ProcessNext Lib "kernel32" Alias "Process32Next" (ByVal hSnapshot As Long, uProcess As PROCESSENTRY32) As Long
Private Declare Sub CloseHandle Lib "kernel32" (ByVal hPass As Long)

Public Function IsProcessActive(ByVal vnPID As Long) As Boolean
Dim hSnap As Long
Dim tProcess As PROCESSENTRY32
   If vnPID Then
       hSnap = CreateToolhelpSnapshot(TH32CS_SNAPPROCESS, 0&)
       If hSnap Then
           tProcess.lSize = Len(tProcess)
           If ProcessFirst(hSnap, tProcess) Then
               Do
                   If tProcess.lProcessId = vnPID Then
                       IsProcessActive = True
                       Exit Do
                   End If
               Loop While ProcessNext(hSnap, tProcess)
           End If
           CloseHandle hSnap
       End If
   End If
End Function  

uses tlhelp32;
function IsProcessActive(const PID: Longword): Boolean;
Var
 hSnap: Longword;
 tProcess: PROCESSENTRY32;
begin
 Result := False;
 if PID <> 0 then
  begin
   hSnap := CreateToolHelp32Snapshot(TH32CS_SNAPPROCESS, 0);
   if hSnap <> 0 then
    begin
     tProcess.dwSize := SizeOf(PROCESSENTRY32);
     if Process32First(hSnap, tProcess) then
      repeat
       Result := (tProcess.th32ProcessID = PID);
       if Result then Break;
      until not Process32Next(hSnap, tProcess);
     CloseHandle(hSnap);
    end;
  end;
end;