I am working on a 'online help desk' project.. I need help to design the initial database model..

Here you are, on a help desk, with the model right in front of you.
You need to specify which part you need help with, not ask for the entire project.
Some sites are not based on interacting with members, just data... WebMD would be an example.

Why redesign the wheel when there are excellent products already available.

One I use a lot is Spiceworks - Free Systems Management and IT Management Software (http://www.spiceworks.com/product/)

Why redesign the wheel I think it's because it's a school project and he needs to know what the typical data entry fields are and figure out how to store and retrieve the data.

You think ;)

I assumed? :)