Error: Link Server in Sql Server2008

Hi

I have two sql server 

A is 2008 R2 and B is 2005

I have created link in A for B.

when I am updating data from A to B

it gives me error:

OLE DB provider "SQLNCLI10" for linked server "LINK_A" returned message "No transaction is active.".
Msg 7391, Level 16, State 2, Line 2
The operation could not be performed because OLE DB provider "SQLNCLI10" for linked server "LINK_A" was unable to begin a distributed transaction.

I try DTC Setting

and 

"EXECUTE sp_serveroption     @server = 'WEBSERVER',
@optname = 'remote proc transaction promotion', @optvalue = 'False' ;"

also it is giving me error

Plz reply any if any one knows the solution.

Thanks