Password Prompt in web browser

#1 - Intranet Zones, firstly look at the servername that is prompting you, make sure something similar is in place in the Intranet Zone, typically the EV Server will have an alias and the actual machine name, it may be prompting you the machine name, but you have the alias in place, or vice versa.

For instance you may have

Alias: EVServer
Actual Machine: myEVServer.myDomain.com

If you have *.myDomain.com listed in the Intranet Zone, and its prompting for a password for EVServer, then you would simply need to add EVServer (the alias) in to the intranet Zone and try again

#4 NTFS Permissions:
This may not apply if you have the "Everyone" permission enabled, how ever on most OS's and most company policies, the drives will be locked down to creator owners, system and the administrators group.

You would set Authenticated Users at the EV Installation directory at the root and have it propogate down with Read, Write and Execute (these are the default three selected when you add a user).
The reason you need execute is that when you go through the web page, IIS takes on Impersonation and it will attempt to run things such as the DirectoryService.exe , and if that user doesn't have permissions you will get the password prompt

#5 Cached Username and Password
This is controled in the User Accounts section, you have a link in the User Control Panel saying "Manage Passwords" and you will have a list of all the servers it has a username and password for.
If you see the EV Server, just try deleting it, as if you have an environment where you have to change your password every 45 days or so, it could be using the old username and password.

But the most important question is, when you enter the username and password, does it work or does it reprompt you for the username and password?