Depends on what operating system you're using.
Windows 7 Pro 64-bit version is the OS.
On a Windows machine, the files are in C:/PROGRAM DATA/ADOBE/PREMIERE ELEMENTS/12.0/ONLINE/.
On a Mac, the files are in MAC HD/LIBRARY/APPLICATION SUPPORT/ADOBE/PREMIERE ELEMENTS/12.0/ONLINE/.
You should also make a full backup of your boot/program drive to an external USB drive
The product I use is at http://www.terabyteunlimited.com/image-for-linux.htm
Image runs off of a bootable CD via Linux (the Zip you download includes a program to make the bootable CD) and it reads EVERYTHING on the drive, even the hidden registration information, so everything is restored when needed... and you may restore the image to a brand new drive in case of a crash, and not have to re-install anything
SG appears to have answered your thread question already.
I have written blog posts about the Content situation for Premiere Elements 11 and 12. If you think that supplemental information would be of interest, these are the links to that information....
Most recent one targets version 12, including attention to 11 user who switches to 12
The following was the first blog post on the topic - information for 11 before 12 was released