Updates
MC has a feature called Check for Updates. You can find it under Help in the program. It checks the web site to see if there are any new, recommended updates. This can be done automatically by setting the interval in options for startup.
The update recommended may not be the very latest. Sometimes a newer version will be available on the download page, but we haven't moved it to the recommended status since it offers only minor changes.
The newest update can always be found manually be visiting Interact, and choosing the board for the current version of MC. At the top of that board, you will find a thread called something like "Media Center X.0.xx -- Available Here". Note, however, that this update is slightly more likely to have unknown flaws. Reading the thread before downloading is always a good idea.
Purchasing an upgrade
Purchase is from within the program, so you first need to install the new version. Here's the download page where you can find it. Visit the Purchase Page to check on upgrade price.
When you install, if your data is from one of the last couple of builds, MC will find it and offer to copy it to a new location where it may be converted to a newer database format. Your old data will be preserved and, for versions from MC11.1 on, you will be able to run your old program, too.
You have 30 days to try the new version. If you decide not to upgrade, you can uninstall the new version.