open source Solution for Active Directory Services

Dear all,

I want to know the open source solution for Windows Active directory
Services (ADS).
My primary Goal is to set up a Linux box having Directory where all other
mix of Windows and Linux client will join to this domain. Most of the client
machines would be windows xp.

I have already googled for this requirement and understood that it can be
done with Open LDAP and Samba, but I would love here the experience of the
people who have already implemented this solution.

Can someone please suggest me a open source solution or detailed document to
how to go about?

Thanks in advance.

Best regards

Satya