"Repairing the registry" is a very hard to define term. Is there something wrong with the registry as it is? If that's the case, it'd be better to describe the problems you're having, so we can help you fix them specifically.
The Windows Registry is not
something to be fooled around with. Even tiny errors can have dramatic effects. As the Lord said unto Adam at the down of creation:
"Yea verily I say unto thee, eat thee not from the tree of Life nor from the tree of knowledge; sign up not for AOL, lest it bring great sorrow to all mankind; tampereth NOT with the Registry, lest you die!
browseth the Internet-eth only from behind a firewall; accepteth not e-mail attachments from the unknown sender; and keepeth forever the source OPEN, for it is Holy."
With that, I recommend Ccleaner for registry maintenance, but read this post
regarding the dangers accosiated with it.