Digidesign's DigiRack Ping-Pong Delay is a plug-in that comes with all versions of Pro Tools, as far as I know. I've ran it at least in both Pro Tools 7 & 8. You don't need to take any action to install it on it's own, as Pro Tools takes care of installing all of it's free plug-ins during the initial installation process. The interface of the plug-in is bland and simple, but at least this makes it easy to read and understand. It's got sliders for controlling your gain, mix, delay, feedback, cross-feedback, and a low pass filter. You can either type in your own values or move the sliders back and forth to set your desired place. I don't think that they make manuals for the individual DigiRack plug-ins, but if you're having problems you might be able to find something in the Pro Tools manual.
I'm currently running Pro Tools LE 8 on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I run Pro Tools LE 8 with a Digidesign 002R audio interface or a Micro Box if I'm on the go. I always run Digidesign DigiRack Ping-Pong Delay and other delay plug-ins on auxiliary tracks to save processing power, but either way this plug-in doesn't take up much processing power anyway. I generally use other delay plug-ins before this one, so I haven't exactly maxed it out to it's full potential, but since all Pro Tools users have this already, all you need to do is simply try it out for yourself to see how well it runs within your system.
For a free plug-in, the Digidesign DigiRack Ping-Pong Delay actually has a pretty clean sound quality. It isn't the warmest or fullest sounding delay plug-in out there by a long shot, but for a freebee it is certainly more than adequate. You can definitley get some really cool ping-pong tones without having to mess around too much with it, so in this sense it's nice to have some quick and easy ping-pong delay. I'd definitely encourage all Pro Tools users out there to give this plug-in a whirl...