The "console" Administrator does not have a password, unless you set one.
You should be able to use the repair console by booting to the XP CD, if you have a real one, and not a restore CD that most manufactures love to issue.
I personally do NOT suggest anyone, unless an employee of MS, even bothers to fire up the command console ... you really need to know what you are doing and its command structure is very basic.
The lsass.exe system error could be the work of a virus, I doubt this, you can replace lsass.exe from a backup.
Have you tried getting into safe mode, F8 at boot ?
An easy alternative is to do a "dirty install" this just re-installs XP and leaves your data intact, some programs may need reinstalling, but again, your data will still be there.
Good luck!
oh, welcome to the forums