I've forgotten many of the Mac OS classic tricks. How to tell which extensions are in use?
The friendliest way to do this (friendly towards the system), is by using the "extension manager" control panel. Using it you can also set different sets of extensions for different usages. Obviously you need to be able to boot though. Otherwise everything in the System Folder/Extensions loads.
I have a GeForce4 MX (32 mb) in my MDD 867, and it works like it should.. I have a french version of the 3.5.2 6 extensions (back in the days you could just go to
http://download.info.apple.com/Apple_Support_Area/Apple_Software_Updates and wander around) I can zip the 6 for you I guess.
As for extensions go. There's a great little util that's called ConflictCatcher. It just takes over Extension Manager and will boot several times with different sets of extensions enabled, simply asking "is problem x still happening"? until you can pinpoint x problem. It's simple but very useful. Once the problem has been resolved you can switch back to extension manager, or you can keep it if you want to see tons of labeled extensions when you boot.
I have a ATI Radeon 9000 pro on my other tower (that's a gigabit ethernet dual 500) and it's nice and all. The only problem I can think of with it is the normal apple repair cd doesn't recognize it.
Regarding extensions for it, in my own experience, the "ATI Rom Xtender" is always causing problems. The pre installed ATI Graphics Accelerator (from 9.2.1. or 9.2.2.) is also problematic with it. If you keep it installed you have to force quit rightaway upon first reboot just to get to the basic settings wizard thing.
Basically I just take those 2 out of the Extensions folder before first reboot, until you can install the extensions with the cd that came with the graphics card. I'm not sure if it's the CD or some other install update but I remember I had to manually take out the extensions on my french system because the installer was a bit stupid.
I have a radeon 9000 update from 2002 and the ati-retail-9-2-2-jan2005.hqx update available if someone needs those, but I'm a total newb here and don't know yet how to handle files.
One of these (or the CD) installs a Control Panel called "ATI Displays" which I suggest to temporarly disable (it's not that useful), when you install multiple applications. The problem I had with the Control Panel is that it would not turn off when installers want to close everything before installing. Simplest way to deal with that is to manually put it in the "Control Panels (disabled)" folder and reboot before installing multiple apps. Or you can each time open the control panel and turn it off.
Then you can put it back where it belongs.