Thanks a lot for your reply.

I try your script this morning, returned the same ERROR above.
But at the other side,it works when i run the script below:

Update [Wlrcserver].Newexec.dbo.Customers_CoypTest
set Unitname=b.Unitname
from [Wlrcserver].Newexec.dbo.Customers_CoypTest a join
Newexec.dbo.Customers_CoypTest b
on a.Cid=b.Cid and b.Cid='Tony'
(1 row(s) affected)

I use SQL Server 2000 with SP4 at [Wlrcserver],and SQL Server 2000 with
SP3 at [HP-server].
Both sides the OS Version are Windows advanced Server 2000.
And I installed MDAC 2.7 yesterday,it didn't work.