I take no responsability with how you use this information. You must own a TI89 titanium calculator to legally download the OS for it. This guide will show how to install the TI89 titanium emulator on a computer running windows XP.(I am not sure what other windows versions it works on) You need to download these three(3) files below and install them in the order of 1, 2. You load program 3 when you run the emulator. 1. http://prdownloads.sourceforge.net/gladewin32/gtk-win32-2.6.8-rc1.exe?download 2. http://www.ticalc.org/pub/win/tiemu.zip Go to http://www.ticalc.org/archives/files/fileinfo/370/37014.html and click tiemu.zip to download if the link above does not work. 3. http://education.ti.com/educationpo...jsp?applicationId=6009&contentPaneId=4&cid=US Scroll to the bottom of the License agreement page to download the TI89 titanium OS and save it to your hard disk. TI89 titanium user manual:http://education.ti.com/educationportal/appsdelivery/download/download_eula.jsp?cid=us&displayMode=G&applicationid=6128&contentpaneid=17 Now that you have GTK+ and the TI emulator installed, open TI emulator and select "You have download a FLASH upgrade on the TI website" and click ok. Go to where you saved the TI OS and open it and it will install the OS on the Emulated calculator. Now you should have that 150 dollar calculator you bought emulated on your computer and should look like this. Have fun playing with your Emulated TI89 titanium calculator!!! Enjoy!!!