Itunes not available in iPhoto for slideshow since Yosemite update

Question

I updated to Yosemite yesterday.  Today I can no longer find iTunes when trying to create a slideshow in iPhoto.  Mac suggests I open iTunes before continuing but iTunes is open.  I have searched and this prompted me to find library.xml file and drag to desktop but there is no library.xml file in my iTunes folder, there are others though.  I have switched them on and off in different orders and I have turned the mac off too.  I have a wedding slideshow coming up soon and had just about finished putting the music to the photos, this is very irritating and stressful.
Thanks for any help you can give me.

Answer 1

It is always a good idea to backup your data before upgrading, and especially before doing anything mission essential.  Did you backup your data before?
If not, piecemeal downgrading is possible, though not as easy without a backup:
http://discussions.apple.com/docs/DOC-1948
It is probably best to wait to upgrade until you know that all your mission essential programs are Yosemite compatible.  You can try Yosemite on a separate partition if you so desired, and then only upgrade when you need to.
The xml file in question may also be in the Music folder in your Users -> yourname folder, or the hidden Users -> yourname -> Library folder. To enable hidden folders, download the utility Tinkertool:
http://www.bresink.com/osx/TinkerToolSys4.html
P.S. Mac is the name of the computer, the operating system, but not the company.  You don't call HP, Pavilion, so why would you call Apple, Mac?
Yosemite has nothing to do with Classic.   The place to ask questions about Yosemite is here:
OS X Yosemite
where I've asked a moderator move this thread.