If you are looking for a cost effective help desk software, then you should look into the open source community. open source means free, no cost, no money. open source software is licensed under the General Public License ( GPL ) and you get the source code along with the software just in case you want to do modifications or further development - you have complete freedom. there are many help desk application licensed under the GNU license, here are four of them I think are cool:

Slick -Ticket. licensed under the GPL license, it guarantees you have the freedom to do whatever you want with it. the application is fully customizable with the option to change themes or create your own using the theme maker - you have the option to import or export themes also. Slick Ticket integrates with active directory so you don't have to create user accounts for your help desk users - grab their credentials directly from active directory. don't be scared by all these jargon you probably don't understand - slick-ticket is very easy to use and install. it requires SOL 2005 or SQL Express and .NET 3.5 in order to work.

osTicket - open source, light weighted support script that can compete with any commercial support app in features. it supports ticket logging by email, web form and via phone by staff. you can also choose to auto reply users with custom messages when submitting a ticket - you can also predefined auto answers for frequently asked questions, cool ah. no sign up require for users needing to submit tickets, they just visit your web form or send an email and there they go. all support tickets are archived for easy retrieve records. osTicket requireds PHP 3+ and MYSQL 4.4+

GLPI - is an inventory and issue tracker software licensed under the GNU license, so you have complete freedom over it. you can track desktops, laptops, printers and other network devices, as well as track user submitted trouble tickets to any IT support group. it supports mail notifications among other things.

OTRS - is another open source help desk application that allow users to submit trouble ticket requests via email, and phone calls. It follows a clear design, yet completely modular and easily extensible to adapt it to individual needs. OSTRS is a huge system with many features not even found on commercial help desk applications, it runs on Linux, Solaris, AIX, FreeBSD, OpenBSD, Mac OS 10.x and Windows.

There you have them, four robust open source help desk applications to enrich your help desk department without breaking up your budget.