It might be a missing path to your Everquest2 install in the registry. Its an easy fix.
Create a new text file and copy\paste the following into it;
Code:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\Everquest2.exe]
@="c:\\program files\\sony\\everquest II"
"Path"="C:\\Program Files\\Sony\\Everquest II"
Save and close the file then rename it eq2Path.reg.
Now double click to enter it into your registry, all this does is add a path to the default install location for EQ2.
Re-run the installer.