- What happens (does it bounce, do you get an error message, what do you see) when you open iPhoto from Macintosh HD > Applications?
- What version of the Mac OS are you running? (Apple > About this Mac)
- What version of iPhoto are you running? (Macintosh HD > Applications, click on iPhoto once and then go to File > Get Info)
While you answer those questions you can try troubleshooting:
1.) Remove the following to the trash, restart the computer and test iPhoto:
Your User > Library > Preferences > com.apple.iphoto (there may be more than one, remove them all)
Your User > Library > Caches > com.apple.iphoto and / or just iphoto
Hope that helps.