we have a set of about 3000 users that used to access our moss site from
accounts we set up in our domain, so domain A, users would log in using VPN and
the usernames and passwords we created for them. Now we have merged companies
and they can now access everything internally(we joined domains no more need for
VPN) so they want to start using there domain B to access MOSS.

So the company in domain B has mysites, access to the correct sites and
everything but moss is using there domain A account, is there an easy way to
merge these accounts so we don't have to go and add all 3000 users to the new
sites and create new mysites?

Does this make since?