I started with a Joomla 1.5.23 site and upgraded it with a joomla 1.5.x – 1.5.26 package from the Joomla website. I went to jEvents to get an updated version. I decided to google jEvents joomla 1.5 upgrade and found this link from jEvents.
Starts with a jUpgrade or simular migration to 2.5. Start by going into plug-ins and enable Moo Tools Upgrade. Then install and run jUpgrade. I have had a lot of difficulty getting jUpgrade to run smoothly in WAMP. I have finally figured out a good install method after a couple of Win 7 reloads and multiple attempts to get WAMP set up with CURL correctly. Here is link to how I did it.
Follow this lesson and got it all up and running in 45 minutes. Basically did jUpgrade, ran their migration php script, and then installed jEvents 3.0 and all the old info was in the new database.