First,
check this thread on the upgrade cost and stuff...
Then... You can download the current "shipping" version of MC here:
http://www.jrmediacenter.com/download.html That's not always the most recent version, but it should always be very stable and usable. If you want to get the most recent version, just go to the
Media Center forum, and look for the most recent build thread (which should be right at the top). Right now, the current build is
11.1.184.
Once you've downloaded the new installer file, just double click on it and proceed through the wizard to install it. MC will upgrade your library automatically, but be aware that once it is upgraded you can't "go back". If you think you might not want to keep the new version, I strongly recommend that you back up your library data files (just the database files, not the music files themselves)
before you upgrade!!! If you're not sure how to do this, just ask and I'm sure someone will help (I don't remember how with a version that old). Anyhow, after you do the upgrade you have a 30 day trial, after which you will need to purchase the program (at the upgrade price) to continue using it.