I am developing a web page in asp.net

I have a webform which uses a connection to an sql server 2000 database residing on the local machine.

Whenever I try to connect to the database I get the error message :

Login failed for user 'DELL\ASPNET'.

I can view the database in Server Explorer and have succesfully tested the connection.

Does anyone have any ideas?
I know nothing about sql server, in access it was always easy.