How do I downgrade an iPhoto library from version 9 to version 8.1 I recently acquired an older Mac and am trying to copy an iPhoto library from a newer computer to it.  However, the older version of iPhoto refuses to open, telling me "You can't open your current photo library using this version of iPhoto... Pease quit and use the latest version of iPhoto."

However, upgrading to the latest version of iPhoto isn't an option.

I found some information suggesting I could downgrade a library to an earlier version of iPhoto.  However, it says to use the "Rebuild Library" command from the "Library" menu.  However, there is no such menu in my version of iPhoto.  I found an Apple on rebuilding the iPhoto library (http://support.apple.com/kb/HT2638) but the option that I seem to need: "Repair the iPhoto Library Database" does not appear in the "Rebuild Photo Library" dialog box I get on startup holding Command and Option, although the "Rebuild the iPhoto Library Database from automatic backup" appears but is grayed out.
I know your pain. I have a 2006 iMac 24 inch and up graded to version 9 iPhoto and every thing went haywire when I opened the program (pixelation, blank screens, frozen screen etc.) I dealt with Apple help over the phone for over 8 hours over a couple of days. They took control of my computer and took snapshots of various screens and sent to their IT for analysis. They got back to me about a week later and said version 9 is not compatible with the GeForce 7300GT GPU. The choice was downgrade to my previous IPhoto version or upgrade the vid card. I chose for the downgrade. The Apple tech took over my screen by remote and spent close to an hour doing wizardry and got it done. BTW He did not lose any of my pictures either. I guess although I provide no help with your problem since the tech did all the work (and I really know nothing) I want you to know there is a solution to your problem out there, somewhere.
Sorry I can not be of more help.
Oh yeah Apple gave me a full refund for the iPhoto ver 9 that I purchased. Apple Help line did everything possible to help me and I was impressed with there attitude and effort.