string还是长整型?

procedure TForm1.BitBtn1Click(Sender: TObject);
var
a,b,c:string;begin
a:=('E:\Games\魔兽争霸\war3.exe');
b:=('E:\Games\Warcraft III\war3.exe');
C:=('D:\Games\Warcraft III\war3.exe');
    if FileExists(a) then
        ShellExecute(handle,'open','\\host01\game02\game\war3map.80.bat','','',SW_SHOWNORMAL)
    else
    if FileExists(b) then
        ShellExecute(handle,'open','\\host01\game02\game\war3map.80.bat','','',SW_SHOWNORMAL)
    else    if FileExists(b) then
        ShellExecute(handle,'open','\\host01\game02\game\war3map.40.bat','','',SW_SHOWNORMAL)
    else
        showmessage('找不到文件');end;
{//****************************
if FileExists(a) then
if FileExists(b) then
都无法执行,路径没有问题!