If you are trying to keep your applications open source and free I would highly recomend using Spiceworks. It is a full fledged administrators tool but it also has a helpdesk funciton. You can customize it as you like and make it do exactly what you want.
You can check it out <a href=”http://www.spiceworks.com/”>here</a>.
This is from Spiceworks site about their help desk features:
ooking for simple but powerful help desk software? Something that lets you manage user tickets, organize your work, and assign tasks to your helpdesk team?
* Receive tickets via web or email
* Assign tickets across your IT team
* Create tickets while browsing network assets
* Track tickets by user, asset, due date & more
Spiceworks is completely free…and you can get started in less than 5 minutes. <a href=”http://www.spiceworks.com/signup/thankyou.php”>Download free help desk software now.</a>