Unstable charts size
 

I am using in excel 2007 some charts developed in 2003 version; they are
positioned in a single chart sheet (used..location ..option); at the first
opening in 2007 I observed they were all contracted in size, and some of them
missing (or too small to be found even at 400% zoom); after re-arranging,
tried to fix their dimensions using "lock aspect" (looked around for another
option but didn't find); finally, charts seems to be on their own, as their
size is shrinking even while working in another sheet!

Maybe there is someone to know a hidden option/command/trick in order to
"freeze" them on my need! Thanks!