I don't get it?

a little off the subject but I have iMac DV 500MHz 384MB RAM 30GB and it runs slow as hell (in os 9) well for games I open something like cro-mag rally and setting everything at its lowest it still uns way too slow to play?
Geez, my imac is 100mhz slower than yours, and cro-mag as well as every other latest game runs great. Try these things:

de-frag that 30 gig drive of yours (with a tool like norton)
turn off unneeded extensions. I have an LAN gaming specific set
rebuild your desktop (cmd-option on startup)
also run norton and make sure you don't have any drive errors

then play your games again :)
Assuming you follow the suggestions above, and it still does not improve...

You might want to open up the computer and check to see that everything is solidly connected. You RAM is obviously working, but it may not be firmly sitting in it's socket.

Also check to see if the heatsink is attached correctly. It could be an issue of overheating. Since you are using OSX, open up the CPU Monitor in the Utilities folder, and set it up to display on the side of your monitor. If it is constantly peaking out even at idle, there might be a hardware issue.

And if the computer is still under warrantee, call Apple and have them check it out.
Make sure you have OpenGL drivers for your graphics card installed properly. If not, you will be using software rendering, and that would be slow on a dual 800 G4 as well. . .