Penetration Testing: Where are Windows "Enforce password history" passwords stored?

[Charles Gillman <charles.gillman () gmail com>]

Can anyone tell me where the "remembered" passwords are stored when
the "Enforce password history" is set in Group Policy?

If this setting is set to its maximum value of 24 then I would expect
24 password hashes are stored for each account for the setting to
work.  But where?

More importantly are there any tools/techniques for accessing the
"remembered" passwords?

Thanks
CG