Cannot run AdPrep on domain

I hope this is the right community to post this in.

I have a domain that I need to run adprep on, but it errors out with numerous errors like below.

OID "1.3.6.1.1.1.1.0" defined for object CN=Vintela-uidNumber,CN=Schema,CN=Configuration,DC=xxx,DC=xxx,DC=xxx conflicts with the schema extensions needed for Windows 2003.

[Status/Consequence]

Adprep will not extend your existing schema.
[User Action]

Contact the vendor of the application that extended the schema with the OID value "1.3.6.1.1.1.1.0" and resolve this inconsistency.  Then run adprep again.

This domain was 2000 and is now 2003 R2, but I cannot add a DC until I run adprep first.

Is there something that I can do to resolve this?

Mark