My friend offer me to install speedyfox to accelerate firefox launching and i gave it a try.
About firefox all i can say - it really works.
But(t) also it optimized my Skype
first time on my pc i left skype on and after optimizing it lost all the groups, list of last discussions and don't want to load history also it lost one contact which wrote me while i did it all and everytime i tried to open discussion skype crashed. i realize that it can be my own fault, but after reinstallation skype still doesn't have groups, history and list of last discussions. the lost contact is back and have no more problem
than i've tried to do the same on my notebook, but this time i switched off skype. this try was much better - only i've lost - groups also in list of last discussions there are all the discussions except two ones i've converted to groups so i can't do it again
when i open skype at home i see alll the groups and all the messages i've sent from my "first try pc"
in conclusion - i think deleting groups is not the part of optimizing