I would actually recommend that you contact Apple. Since they transferred your media (from a PC?), they are responsible for making sure that the files are in the appropriate locations. It sounds like that's not the case for the photos. If you haven't actually done any work in iPhoto yet, the simplest procedure might just be to start afresh and copy all your old PC photos into iPhoto.
Matt, trhanks for the suggrstion, however my Imac is 18 months old, and I have upgraded to Lion so not sure exactly where problem was createt. I have also added many hundreds photos on iphoto sence. I wanted to copy the iphoto file to another hard drive when I discovered photos are not were there supposed to be.
Now i wonder if my time machine back up is getting my photos backed up or not.
Can i create a iphoto file and drag my photos to this file???
Still need help
OK, so just that I understand the situation. You bought a Mac with 10.6, and it was updated to 10.7. Can you explain at what stage the Mac store transferred your photos, and from where? When you upgrade from (for example) 10.6 to 10.7, it shouldn't require ANY moving of photos.
Do you still have the iPhoto application, at least? (Check in the Applications folder).
Try searching on your drive (using Spotlight, at the top right of the screen) for "iPhoto Library". You could also check your Time Machine - go into the TM interface (Enter Time Machine from the menu icon, don't just open your external drive) and look in the Pictures folder at several points in the past. See if you can identify when it was present, and when it disappeared from that location.