If that doesn't help, see if you have the StuffItCM.plugin (in /Library/Contextual Menu Items)
If you do, move it out of there to the Desktop for now and see if it corrects the problem.
Trash the 'com.apple.finder.plist' file located in User/Library/Preferences
Restart
Run Repair Permissions from Disk Utility in your Utility folder.
Download one of these;
Onyx, Yasu, Cocktail
Use to clear all Caches, run maintenance scripts, etc.
Apple does make it easier to reinstall these apps. See Custom Installs
With systems prior to 10.4, you could use Pacifist to extract these apps from the Installer disc.
Yes, try the Keychain First Aid.
I only have one System in my Keychains. Don't know why you would have two.
Look here;
Library/Keychains
If there are two in there, drag one to the desktop, don't trash.
Look at the date on each and drag the older one out.
Restart and see if that makes a...
Try trashing the com.aoole.systempreferences.plist located in; Users:YOU:Library:Preferences:com.apple.systempreferences.plist
I would also run Repair Permissions from Disk Utility in your Utility folder, then boot off your OS disc and run Repair Disk from Disk Utility.
Open Keychain Access. Under one of the Menus there's a Repair Keychain. Try that.
You could also download and run the 10.3.9 Combo Updater and see if that helps.
You could try resetting the CUDA chip.
On the Logic Board, next to the battery there are two small buttons. The one closest to the battery is the CUDA button (S4). Disconnect the power cord. Press the CUDA button once for a second (only press once). Close it up and see if it boots.
You can't download 10.4, you can only download the free updates from Apple for 10.4.
You have to buy a retail copy of 10.4 (Tiger) to install.
You can just use the upgrade method when you get the Tiger DVD and you won't lose anything.