How to call a sharepoint url with credentials from asp.net

[kummss]

I have an asp.net application, from which I want to open a sharepoint site url with username, password and domain name.

I have tried using xmlHttp and ActiveXObject. It is working fine when I directly run the project from my system and click the link.
But after configuring my application in IIS - virtual directory, when I access my application from different machine by using my ip address, its not working. It means, when I click the link, the page simply got refreshed. Nothing happens.
This is the code I am using...

xmlHttp = new ActiveXObject("Msxml2.XmlHttp");
xmlHttp.open("GET", spDefLoc, false, spUserName, spPwd);
xmlHttp.send();

I have already searched more sites but couldn't find the right solution.
Is this a right approach? or Do I need to follow any other techniques?

Thanks in advance
Kummss