I use MacCaption (the Macintosh version of CaptionMaker) from http://www.cpcweb.com on a daily basis. It is very good software for captioning, and the folks from CPC are fantastic! The software uses a USB dongle key and you can move this key from machine to machine (Windows and Macintosh too!) This allows you to have the software installed on several machines/platforms. When you need to use it–you just make sure you have the USB dongle on that machine to run it. You pay one time for their software, and then you have access to the updates whenever you want them.
I choose to use the Macintosh version of the software because the Macintosh version of the software was designed for a graphical user interface. The Windows version (I think anyway) looks too much like DOS. (I also have access to both platforms.)
Give them a call and tell them what you want to do, and I am sure they can help you. They are very good folks to work with.
Chuck