I have lost access to the root of the boot partition, now I can't logon.

Logon to the NT machine as Administrator

When you get the blue screen and "Path too Long" press the OK button

Press Ctrl-Alt-Del and the Windows NT Security dialog box will be shown

Press the Task Manager button and the task manager will be shown

Select the Applications tab and click the "New Task" button

Enter the path "%systemroot%system32cmd.exe"

Enter the command
CACLS d: /e /g everyone:F
where d is the boot partition

Select Task Manager again and click "New Task", and enter %systemroot%explorer.exe, the desktop should now appear

Logout and login again to confirm everything is OK

You should now set the permissions on the root, see Q155315 at http://support.microsoft.com/support/kb/articles/q155/3/15.asp for more information