having two different domains that direct to one hosting

Hey guys

im in a bit of confusion right now, let me start from the start:
1. client wants a redesign he already has hosting and a domain.
2. he gets the redesign and a new name and domain also hosting.
3. we redirect the old domain to our new hosting.

example ( old domain "snowon.com" new domain "justanexample.com")
we redirected the first one to the new one.

What happens now is that the old domain has indexed alot of the files on the new site.
But the new domain hasnt indexed anything at all (except the front page) which is as you can imagine a pain, i have submitted a sitemap to google, before the indexing on othe old domain started.

Why has this happend? and is there any way of reversing the process, or is there any disadvantages of having an old domain indexing the files, can you have both domains indexing the files?

lots of question hope to get some answers thanks :)!

you can do two things:

removing all old URLs from google via the webmaster tools

or you re-write the old URL's to ne one (the last might be better)

You just need to change the domain to use the new nameservers.

just link build and promote your new url.