Can you be more specific on what you're trying to do? That hardly describes the problem at all. The one thing you need to do to get help is describe your problem as thoroughly as possible.
Are you trying to password protect a portion of your website? Do you want to change the default account IIS uses to run?
Basically IIS is set up to run under the User account IUSR_<machine-name>, where <machine-name> is the name of your computer. IIS usually controls the password, for security reasons, and you should let it, unless you don't want anonymous users to view your website. You can specify any other account to use to run IIS, just create a user and go to the IIS snap in and somewhere under security specify that account.
If all you want to do is password protect an area of your site, like a folder or file "default.html", just right-click on the file/folder, select properties, and on the security tab make sure the account IUSR_<machine-name> doesn't have any permissions. On the other hand, make sure that some other account has at least read permissions. If you access the folder/file whose security settings you've just edited you will get a Login window. Type in the info for a user with at least read permissions and you will view the file/folder.
