Well, I think the title says a lot. I promised in another link to provide some info on a free help-desk software. It is the one we use where I work (customized). The software is free for up to 3 technicians and allows for a lot of personalization out of the box.

Basic info:
Platform: Windows OR LINUX
Provider website: Web-Based Help Desk Software Solutions - Internet Software Sciences
Registration: Simple email based, I've not received any emails from them in the 2 years that I've had the software (including when we were researching and testing at work)
Package: Web+Center 5.0
Fee: Free for 3 or fewer users
Code Base: ASP
Database: MDB (Microsoft Access) or SQL (Don't need access to use the software)
Setup time: 2 hours or LESS
Personalization time: EXPECT A LOT, the administrative side has many options.
Modules: Technician, Business contact/billing, Customer, portable user
Documentation: Very VERY good, install instructions include screen shots, step by step instructions, and it will test most required settings using an asp based install test script. If you can't get it up and running with their instructions (which would amaze me that you can't), you can always pay for their support, we have used it a time or two at work (using IIS 6), and it has been professional, rapid, and extremely helpful.
Other features: Asset Tracking, Customer Tracking, Knowledgebase, Email notification (needs smtp or other mail server info)(html or plain text), time on call, reports.

I just this evening reloaded this software on my server this evening (after I reloaded my whole machine). So if you want to see a default install you can use the demo on the ISS web site. I stress the 2 hours or less initial setup if you have even a basic idea about web applications, their instructions are very good, and may take more, if you take your time to digest all that is said, but if you just follow the step-by-step, you won't need to understand very much at all.

Some customization tips. When creating virtual directories in IIS, you can rename the directories for 5 of the 6 physical directories. Such as, I renamed the virtual directory for the "customer center" to "support", making my customer side easier to remember. However do NOT rename the languages directory. Many images are stored in that directory, which have static references in the other modules, thus the recommendation to name the virtual directory "Language50" should be followed.