If you are running a Mac that does not have an infrared sensor (such as all the older Macs, or even the latest Mac Pros), you cannot run Front Row out-of-the-box on Tiger. The Keyspan Front Row remote also does not work.
In fact, many of the the Macs running Tiger that do not have a built-in IR sensor do not even come with Front Row pre-installed. The big exception is the Mac Pro, which comes with Front Row pre-installed with Tiger (but it does not run, since it does not have a built-in IR sensor). Note that if you upgrade to Leopard, Front Row is installed and runs, even if your Mac does not have a IR sensor (just use the keyboard to navigate). If you want to use a remote (and your Mac did not come with one), the Keyspan Front Row remote is one option. Just plug in the USB RF sensor that comes with it into a USB port, and use the RF remote. It's that simple!
But if you want to use Tiger, Front Row (with or without a remote) will not run unless your Mac came with a built-in Infrared sensor. There are a number of solutions to get Front Row to run on these Macs running Tiger.
Before we start, note that if you are really lazy, you can download a program called Activate Front Row from MacUpdate. Apparently, it does all of the following for you. However, I am always a little nervous with closed source software that installs kernel extensions. With my approach, you manually install an open source kernel extension, which is safer in my view. Here's how to do just that...
[robg adds: I would agree with the above statement on Activate Front Row -- somewhat strangely, there's no home page associated with the software that I can find anywhere. Download links on MacUpdate, Softpedia, etc. aren't linked to a developer site. With something as low-level as a kernel extension, I would be a bit hesitant to install such code without more information about where it came from. The step-by-step solution below is definitely a safer solution, even if it does require more work.]
First, you will likely need to install Front Row on your Mac running Tiger (unless you are using a Mac Pro!). You can download Front Row (version 1.3.1) directly from Apple. But Apple has crippled the installer, so it will not install on Macs without an IR sensor.
There are ways to get around this, but depending on where you live, you might be violating Apple's copyright or license agreement. Check your local laws first. If it is legal, then check other hints on this website or use Google to find out how you can install the Front Row software. (Since I was using a Mac Pro, I did not need to install Front Row. It just doesn't work).
Second, you will need to fool the Mac into thinking it has a built in IR sensor. (Unless Front Row sees an IR sensor, it will not run). Once Front row is running, you can use the keyboard to navigate the menus, or use a Front Row capable remote. There are three ways to fool Front Row into thinking your Mac has a built in IR sensor:
sudo touch /System/Library/ExtensionsMac OS X Hints
http://hints.macworld.com/article.php?story=20080226125010885