Go to the start menu and click 'run.' In box type "msconfig" and then navigate to the right most tab, labelled 'startup.' Have a look through the list of things that start at startup and see if you can find an entry that belongs to this program - the filepath should give it away. When you've found it just untick it, restart as prompted and on startup put a tick in the box to hide the message and click OK (or whatever button it is).
If you can't find it there then it could be in the startup folder in the Programs list.