Hello, I'm using the download version of Music Maker 16 (I bought the real thing but installed on an old computer that physically broke)

I'm not very technologically-smart so I have no idea what to do. My computer forced me to upgrade from Windows 8 to 8.1. When it finished and I tryed to open MMM, it said:

"The program could not be started. It's possible that the installation folder is damaged. 

Reinstalling the program could remedy the problem. Error code 6"

(If I click ok or close the bubble, the program immediately closes)

If I reinstall, will I lose all the projects I've worked on? I stupidly did not back up anything (which I will definitely be doing from now on!)  It's also apparently impossible to uninstall 8.1 and go back to 8. 

I also have REAPER installed and it's working fine. (I'm also in Canada, although this site won't let me choose that as an option. I'm not sure if that's important or not, but just in case)

If anyone could help me in any way I would appreciate it immensely, thank you!