I recently had to restore an object (user account) in Active Directory that was accidentally deleted. The AdRestore Tool makes this very easy and painless.
Download it here AdRestore:
Once you download and install it... open up the cmd prompt and type in:
c:\> adrestore -r username
c:\> adrestore -r objectname
In my case I needed to restore a useraccount called mbrown. So I ran c:\adrestore -r mbrown the search returned 5 accounts that started with mbrown, I choose no to all but the one I wanted to restore, choose yes to the correct mbrown account and presto... the account was back in the original OU.
Afterwards, I did have to go in and refresh the OU and enable the account... but at least the SID was correct.