This server has a trust relationship
Windows Small Business Server 2003 Setup cannot continue because this server has a trust relationship. Windows Small Business Server does not support trust relationships between domains.
To continue Setup, remove any trust relationships to or from the computer on which you are installing Windows Small Business Server 2003, and then click Check Again to refresh the list of Setup requirements.To revoke trust relationships
Click Start, click Run, and then type Domain.msc.
Right-click the name of your domain, and then click Properties.
On the Trusts tab, click a domain name in either Domains trusted by this domain (outgoing trusts) or Domains that trust this domain (incoming trusts), and then click Remove.
Repeat step 3 until all trusts are revoked.