Not sure if you're still having problems with this (and hopefully this post might help someone else in the future), but you basically have two options to install the client:
1) An ISO is a disc image file. You could double-click each .iso file and let Windows Image/Disc Burner (or whatever it's called) burn each .iso to a CD. This program is only included with Windows Vista and Windows 7, no older versions of Windows. You would then use those CDs to install the game the way you normally would if you purchased the game from a store.
2) You can mount each .iso to a virtual drive and install from there. There are many programs that can do this, but my favorite is MagicISO/MagicDisc. It's freeware and can be found
here. Basically you install the program and it drops a little disc icon into your system tray. Right-click on that icon, go to virtual drive and select "Mount". Then browse to the Disc 1 .iso file. Now, open up Computer/My Computer and you should see a new drive letter under optical drives. Open it to explore the .iso image as if it were a CD and find the setup .exe. Run that, and just repeat the process for mounting the other Discs 2-5 as the EQ Titanium setup asks for them.
Also, I would avoid using DaemonTools or whatever they're calling it now. It used to be a great program but I've heard that they've apparently started integrating spyware into the version they offer now. Desperate for cash, I guess.