Installing plug-ins... Help!

Hi, I have varying success installing new plug-ins on my system, some show up, some don't. What am i doing wrong? My system: Mac Book Power PC OS 10.4.9 Pro Tools M Powered 7.4 M Audio firewire 410 For instance yesterday i downloaded a free delay plug-in (the AU file): Unzipped it and dragged it into my library where all my other .component files are, booted up pro tools and it doesn't show up in my list of effects. I know my way round mac's and pro tools pretty well so it's not a novice thing. I just wander whether it's an issue with my PowerPC not being Intel or an old OSX issue? Or perhaps i'm just installing them wrong... funny how some have shown up and others not though, any ideas? Thanks, YDR

AU = Audio Units, the universal Mac plugin format for applications such as LOGIC, DIGITAL PERFORMER, etc. ProToolsLE uses its own format that is highly optimized for its own environment known as RTAS, short for REAL TIME AUDIO SUITE. You must install RTAS plugins, not AU plugins.

Gotcha! i'm a Logic convert you see and i always understood AU was a Mac format regardless of the DAW.. Much thanks, YDR

And just for the record. RTAS and AU was a bad idea from the start. This was simply a way to try and get a proprietary plugin system and dissolve the VST system an di guess to stop paying the licence fees to Steinberg?. Its what companies do I guess, but it made life a lot more difficult for developers and users. Even Motu got in the act and has their own system as well. Now, if everyone just played ball life would be a little easier for all of us :)