From what I've read, it's related to HP printer software:

Quote:

TrayApp is a software application that is installed with software that is needed for HP printer products used with a computer system. The software that is installed is called HP Photosmart Digital Imaging software, which is used to scan as well as print documents and photos. When any part of the program is removed or corrupted in the registry, a Windows Installer box can appear at start-up.