Hello Irparera,
Actually I have gotten OSticket to work well with Windows 2003 Server IIS. I recomend you do take it in steps. Make sure PHP works fine, then install and configure your SQL server with phpMyAdmin to help create and setup your database files.
Once all of those have been done and are working, go into your "php.ini" file, it will either be in "c:\php" directory or "c:\windows" directory depending how you installed your php to work. Once you are ablet o edit your php.ini file, make sure "Short Tags" are turned on. Just search through the php.ini file to turn on short tags.
Also on the extensions section of your php.ini file, make sure to uncomment, that is remove the beginning quotes from the extensions mysql, mssql, mysqli. This should get you to install OSticket just fine. If you do not enable short tags, your index page will keep recyclying jibberish in the text boxes. You must have an already blank and created database within mysql ready for the instillation program to create all the tables for you.
When mysql is installed on the system, there technically is still not an actual "Database" that you can use to install all the tables needed by OSticket. That is why you need to setup phpMyAdmin, so that you can create a new database for OSticket. I made one simply called helpdesk.
I hope this helps. I have gotten OSticket to work wonderfully. The only thing I cannot do is get my emails to work, but that is something I hope to remedy soon.