sqlserver user

I use sqlserver with my application.
When I install my application on onther computers , I create the database with an install script.

For security I use windows authentication. The sqlserver is installed on a local machine(server)

Now it is only possible to enter my application when I add a new user using Windows authentication and the domain name of my sql server.

Currently I use the standard ASPNET/domainname account, is this OK? And how can I make my own user, it seems that a new user mus first be added at Windows NT level? And how can I refer to that user in my web.config file, because now it seems to ignore the user ID information in my webconfig file?

for example, this is the information in my webconfig :

mode="InProc"
stateConnectionString="tcpip=127.0.0.1:42424"
sqlConnectionString="data source=127.0.0.1;user=dbo ;password="
cookieless="false"
timeout="20"

And the user my application uses to enter the datatbase is the ASPNET/domainname user.

Can anybody explain me how this is working? Thanks in advance!

Krol