Is it safe to assume that at some point, Prior to having your hard drive replaced, you made a backup copy of your internal hard drive to an external hard drive, or USB stick,as is ALWAYS recommended in case your computer ever failed, like this? Or you were using Time Machine? If not, I'm afraid your at a loss of your photos. You might try rebooting your system while holding down the Command-R keys to boot into the Lion Recovery Partition, and there open Disk Utility and run "Repair Disk" after selecting your "Macintosh HD". That "may" help.
Hope this helps
To re-install iPhoto
1. Put the iPhoto.app in the trash (Drag it from your Applications Folder to the trash)
2a: On 10.5: Go to HD/Library/Receipts and remove any pkg file there with iPhoto in the name.
2b: On 10.6: Those receipts may be found as follows: In the Finder use the Go menu and select Go To Folder. In the resulting window type
2c: on 10.7 or later they're at
A Finder Window will open at that location and you can remove the iPhoto pkg files.
If you purchased an iLife Disk, then iPhoto is on it.
If iPhoto was installed on your Mac when you go it then it’s on the System Restore disks that came with your Mac. Insert the first one and opt to ‘Install Bundled Applications Only.
If you purchased it on the App Store or have a Recent Mac you can find it in your Purchases List.
Thanks Radiation and Terence for your responses.
Radiation - I'm mortified to admit that I had neither back or time machine prior to new hard drive. I didn't opt to buy a new hard drive - it apparantly somehow became 'corrupt' and I had to take into the apple store Genius Bar to be advised of this, hence needing a new hard drive. Once I got the computer back home I found I was unable to open iphotos, so I spoke with one of the advisors in store who stated that as when my screen saver was activated it was still showing my iphoto library pictures that I hadn't actually lost them. As I really am useless at anything remotely technical it was suggested that I book another Genius Bar appointment and take my computer back to store. As the nearest store is a 2 hour round trip I decided to ask the question on here first. Sadly I am still at a loss!