Hidden / System accounts

Hello guys, I need a help, please.

I would like to know how do I create a new "system" (or hidden) account on
Windows Vista Ultimate? For example, I noticed that VMWare and the IIS server
create new accounts (__vmware_user__ and IUSR_[MachineName] ) but those
accounts don't appear in my user control panel and, most importantly, they
don't appear in the welcome / login screen and neither on the C:\Users
folder. They only appear in the "Computer Management" console, which is
perfect. I would like to create a new account just to be used by a service
running on my machine so that I can control permissions for that service
(otherwise it will run with SYSTEM user permissions by default).

I tried creating a new account in the "Computer Management" console, but it
will create a new user account that appears in the welcome screen and on
C:\Users folder.

I hope I was clear enough. I appreciate any help. Thank you.

Andre