ok guys,
I have WinRar and just dowloaded 7zip.
I have an Intel core2duo and 2gb of Ram.
I must admit i have used Win Rar mostly to decompress files (works pretty good and very fast). and to compress few things but nothing big (and alos works fine).
I got the message about pictures from russ. thanks

What about the amount of megs or files that is recomended to compress in one file? any number or it has nothing to do?
Is it true or just a legend that you may loose your data on the process to compress and decompress?