If you recently uninstalled, wait approximately three minutes for the settings to get propagated to the Operations Manager database before you reinstall.
If you do not wait for the uninstall to register, reinstalling can result in managed clients that are not listed in the Operations Manager Console.
If you uninstall, you detach the Hardware Management Pack from the Operations Manager Server. You must then reinstall the Hardware Management Pack into the Operations Manager 2007.
See Installing the Hardware Management Pack for more information.