If you are certain that iCal is no longer present on your computer...
To reinstall iCal:
1. Insert the Leopard Installation disk into the computer.
2. The disk will appear on the desktop.
3. Double click on the "Optional Installs" folder.
4. Double click on the "Optional Installs.mpkg."
5. Click on (Continue) in Introduction.
6. Click on (Continue) in Software License Agreement.
7. Click on (Agree) to agree to the terms of the software license agreement.
8. Click on the disclosure arrow ▶ next to Applications.
9. Select (✓) iCal.
10. Click (Continue).
11. After iCal has been reinstalled, download and install the Mac OS X 10.5.8 Combo Update to bring iCal up to the most recent version.
Thank you so much for the help! I sort of followed your advice- I reinstalled from the original osX disk, then ran the 10.5.8 combo updater which brought iCal up to version 3.0.8 which runs! The only issue is, when I open an event, the box is completely black and cannot be read until I go into edit and actually click in the box (Location, from, to, etc.) to add text. Being relatively new o Mac and etremely new to these communities, should I post this issue seperately, in case others are having the same issue?
I have tried to help other users with a similar problem with limited success:
You may want to try the plist/cache removal procedure.
The only other users that reported success replaced iCal using this procedure: Black edit pane: Apple Support Communities.
If none of that works, create a new thread describing what you have tried.
Considering your system/hardware you may want to investigate upgrading to Snow Leopard.