iPhoto library problem.

I recently have been having problems with iPhoto. I imported my photos that I have backed up onto an external hard drive. The photos were as they came from my old computer, just a bunch of folders with dates on them and the jpegs inside them.

Anyway, something obviously has gone wrong and when iPhoto starts up it's giving errors about not being able to read the iPhoto library because it's either corrupt or in use by another program. I decided to simply delete the library file and reimport my files from the external HDD but I can't even get into iPhoto. Even when I hold down cmd+alt and try any of the options, I just an error and have to quit.

The original library file is no longer available as the trash has been emptied.

I have deleted the iPhoto app from the applications folder and reinstalled the extra applications from the Applications Install CD, but the problem remains.

What I want to do is force iPhoto to simply start again from scratch as if it's never been used before so I can simply tell it to import my photo collection from my external HDD.

Any hints about how to go about this?

It's a 27 inch Core 2 iMac with OS 10.6.4 if that helps.