var
   CanUseXvid, XvidInstalled : boolean;

procedure XvidDelete;    
begin
  DeleteFile(ExpandConstant('{sys}\xvidcore.dll'));
  DeleteFile(ExpandConstant('{sys}\xvidvfw.dll'));
  RegDeleteValue(HKEY_LOCAL_MACHINE,'SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32','VIDC.XVID');
end;

procedure XvidInstall;
var
  f:boolean;
begin
  CanUseXvid:=False;    
  XvidInstalled:=False;  
if not (FileExists(ExpandConstant('{sys}\xvidcore.dll')) and
  FileExists(ExpandConstant('{sys}\xvidvfw.dll')) and
  RegValueExists(HKEY_LOCAL_MACHINE,'SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32','VIDC.XVID')) then   
try
  XvidDelete;
  ExtractTemporaryFile('xvidcore.dll');
  ExtractTemporaryFile('xvidvfw.dll');
  f:=FileCopy(ExpandConstant('{tmp}\xvidcore.dll'),ExpandConstant('{sys}\xvidcore.dll'),False);
  f:=f and FileCopy(ExpandConstant('{tmp}\xvidvfw.dll'),ExpandConstant('{sys}\xvidvfw.dll'),False);
  f:=f and RegWriteStringValue(HKEY_LOCAL_MACHINE,'SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32','VIDC.XVID','xvidvfw.dll');
if  f then begin XvidInstalled:=True; CanUseXvid:=True;   
end else XvidDelete; except end else CanUseXvid:=True;
end;

procedure XvidUnInstall;
begin
if XvidInstalled then XvidDelete;  
end;