Error - copying file from one server domain to another server domain

i am getting problem in file copying from one server to another server domain in ASP.NET.

server name 1 : testserver1

Domain name : test

server name 2 : testserver2

domain name : testnet.

see my code :

SourceFilePath = "\\testserver2\fileslst\Reports\New\" & lblRenameGrid.Text & ".pdf"

DestinationFilePath = Server.MapPath("~/") + Session("ENo") & "\" & lblGrid.Text & ".pdf"

File.Copy(SourceFilePath, DestinationFilePath)

Error:

In server , it shows error message as given below:

 Microsoft JScript runtime error:

Sys.WebForms.PageRequestManagerServerErrorException:

The account used is a computer account. Use your global user account or local user account to access this server.

But, the same will work in localhost

how to solve the above error...?