WordPress MU

Can someone help me with this? I have zero knowledge about .htaccess rewrite.
I currently have mail.domain.com, and some other pre-existed subdomain...those subdomain is configured using apache virtual host.
I have installed wpmu to domain.com/blog.
when i create a new blog, wpmu indicated test.domain.com/blog for my new blog.
However, i like users to use *.domain.com instead of *.domain.com/blog.

how to setup the wildcard rewrite for it that does not include my pre-exist subdomain?

thanks in advance
fisherman

reinstall WPMU at root level, not in a directory called "blog".

thanks for you reply MrBrian .... If i have a choice, i will install it at root and save this problem.