You can not reinstall the OS from the BIOS. You must reinstall the OS from an external storage device like a CD or USB flash drive.
You may be able to fix this error. The LSASS is the logon security routine and since the error is saying 'object not found', I would suspect the GINA files are missing. On the DT366, this is the group of files that allow you to logon with the on-screen keyboard.
Can you provide additional data? Did it every work? If so, what happened or what were you doing when it stopped? It's also possible that you have virus. Do you have a backup of the OS when it was working? Do you have the installation CD for your OS? What version of Windows is it - 2K, XPe, XP Pro, XP Tablet Edition - all use the LSASS.
Hopefully, I can provide better advice once I know a little more about your tablet.