1.24 is a full install, 1.25 can be added after that, it is a delta install.
When you get your game powered up, hit the ENTER diagnostic button and look at the lower right corner of your game, that will let you know what version is currently in your game.
Here is the download page for updates and or current manual -
http://support.jerseyjackpinball.com/downloads/woz/
Full system install - directions here -
http://support.jerseyjackpinball.com:8081/helpdesk/WebObjects/Helpdesk.woa/wa/FaqActions/view?faqId=9
Once you have 1.24 in your game, then you can install 1.25 which is a Delta Install, a little different, instructions on a pull down menu here under frequently asked questions, programming software, use the Delta Update instructions.
http://support.jerseyjackpinball.com:8081/helpdesk/WebObjects/Helpdesk.woa/wa/FaqActions/
When you download the 1.24, it can take a good ten minutes or more to load on the memory stick, if it stops at about 24, it isn't stuck, it is going, some of the files are big. When you do the full system install in your game, it takes similar time to load.
The Delta updates goes in faster, about 15 seconds. here is Daniel Tonks video on how to do the Delta Update
http://www.pinplay.com/12/woz_video_tutorial_delta_updates.html
When you are done, anytime you do a full system install, you may want to calibrate the spinning house, here is a nice video that show how to do that from Daniel Tonks
http://www.pinplay.com/8/woz_video_tutorial_how_to_calibrate_dorothys_house.html
At the bottom of Daniel's page are other helpful WOZ tips.
LTG : )