Problems Authentications Reporting Service 2005

[refv8]

Hi im working on aplications with Form authentication where the users
is from a Active Directory in one server inside the Domain, i want to
see using the ReportViewer to see the report hosted in another server
(between the same domain), the problem is that i cant authentication
with the Reporting Service. i would wish to give permisions to the user
ASPNET for not depending of credencial to user himself.
The only way to see the report is give anonymus access with te user
IUSR_MYSERVER, but is to very very insegurity :S

Thanks a lots and sorry for my english.