Sites migrated to DSL holding onto old DNS record

Hello,

We are currently in the middle of a DSL migration project as well as an AD
migration project. Sites are being removed from frame relays and migrated
to a DSL solution. Due to this being at the same time as our AD migration
we modified the DHCP scopes to point to the new DNS servers in our new
environment.

New parent domain: wwit.adecco.net
New child domain: am.adecco.net
Current parent domain: adoint.net
Current child domain: na.adoint.net

The problem occurs when a site is migrated to DSL it is holding on to the
old DNS record in the old DNS server. When I delete the DNS record from the
old domain and do an ipconfig /registerdns from the workstation that was
just migrated to DSL it creates the record again in the NA domain. Could
this problem be because the computer itself is still registered in the NA
domain? Shouldn't the DNS suffix search order determine this?

We have also modified the settings on our users workstations to reflect the
new DNS settings, however because not everybody in the company has been
migrated yet we are also still holding onto the current DNS settings as
well.

So we have set the users workstations DNS suffixes search order:
am.adecco.net
wwit.adecco.net
na.adoint.net
os.olsten.com (older domain)
adoint.net

We have also set the DNS suffix for this connection as am.adecco.net

Any ideas or suggestions would help us out a lot.

Thanks