USB external drive ( Adaptec USB 2.0)

Windows 2000 pro detect the Mass storage device. However, after auto install driver, it comes back saying device will not work properly. Device manager has the warning sign. I un-installed the device and reinstalled it. Problem does not resolved. Drive does not come with driver for windows 2k. Adaptec claim that it included in Windows 2000 pro and XP. I running windows 2000 pro w/sp4.