Microsoft Knowledge Base Article 873160 provides a workaround for an issue that occurs when you install Microsoft Windows XP Service Pack 2 and you receive error message 7391 when a distributed transaction runs against a linked server.

There error message is:

Server: Msg 7391, Level 16, State 1, Line 1
The operation could not be performed because the OLE DB provider 'SQLOLEDB' was unable to start a distributed transaction.
\[OLE/DB provider returned message: New transaction cannot enlist in the specified transaction coordinator. \]
OLE DB error trace \[OLE/DB Provider 'SQLOLEDB' ITransactionJoin::JoinTransaction returned 0x8004d00a\].