Hello Carlos, >I am developing a app for many customs. Each time a make a little (or great) modification of it, must i send to all of them the entire new exe file? or ther's a way to update the existing one ?. Is very important cause the exe file could be higher than >3 Mbytes. Even if i use E-Mail to distribute it time is gold for me and for the others. On my past job we did the following thing. Each time when something were changed we produce diff file which is relatively small and then at client site ran the updating utility. We have been used utility that was written for OS/2 (if I right recall, it was MDIFF).