iTunes not working after update

I tried to buy a song a few weeks ago and it I had to upgrade before buying this certain song-it hadn't done this for any other artist I was just looking at-so I upgraded, and then I still couldn't buy it with my link in my bottom menu. I have a linnk on my desktop, so I opened that, and I was able to buy the song, but once I turned on my computor the next day after shutting it down, it wouldn't open and said: "The file 'iTunes Library' cannot beread because it was created by a newer version of iTunes."
I've since tried re-downloading the newest version of iTunes, but to no avail does iTunes open.
I've tried looking for where to email tech support directly, but seem incapable of finding the link to email them.