Sorry - but your problem is very simple and you were warned about the library upgrade and you accepted it
We can help but if you continue to flail and editorialize instead of follow a logical path it will not be possible
Nothing involves installing a different OS
You have not lost iPhoto 7 - what you have done is upgrade your iPhoto 7 library to iPhoto '09 and when you did that you were told that upgrading would mean that your library could no longer be used by earlier versios of iPhoto - which is exactly what you are seeing
In other words you made this choice - but it can be easily solved
Your choices are
1 - to install iPhoto '09 on your older system (or iPhoto'11 on both) from a purchased iLife DVD,
2 - restore you backup of the iPhoto 7 library from before you upgraded it
or
3 - use iPhoto Library Manager - http://www.fatcatsoftware.com/iplm/ - to downgrade your library to iPhoto 7
Again no mention of changing OS any where in my suggestions
and if you would spend your time reading the links and following the suggestions rather than posting profane and obscene comments you would have seen the IPLM link for older versions - http://www.fatcatsoftware.com/iplm_downloads -- since you never bothered to even mention the version of the Mac OS that you have how would expect anyone to know what you have - we are not mind readers
Remember you created the problem and you are working with volunteer users who really do not care a bit about Windows because we are Mac users - if you like Windows better then go use it - editorializing about it here does nothing to help you or help us understand your problem
LN