It's sort of hard to diagnose your problem since you provide so few details. At what point do you encounter the significant slow down? The spinning beach ball sounds like the loading of 9.2's network stack, which is totally normal.
Here's what you should note in order to successfully diagnose the issue:
1) How long does it take to turn the monitor on and find the startup volume? In other words, how long, from the time you turn the machine on, does it take for the Happy Mac to be displayed?
If it takes a long time, you have some hard drive and/or system software corruption. I would go to Alsoft
and purchase Disk Warrior, the best disk utility software money can buy. And optionally I would clean install the system software.
2) How long does it take for the Mac OS: Starting Up progress to complete?
If it takes a long time, you have to look at your extensions. Go to the Extensions Manager control panel, duplicate your current extensions set, and then select "9.2 All" in the Selected Set menu. Restart, and then begin to enable certain sets of extensions that you need or wish to run.
3. How long does it take to load the Finder (after the startup screen disappears)?
If it takes a long time, you may wish to a) rebuild the desktop (hold the command and option keys before you get to the desktop and keep them held until you get the dialog); b) run Diskwarrior (highly recommended); c) clean install the OS.