Can't merge

when i try to merge 2 avi files dvdfab stops responding can some help please i am running win vista home

dvdfab will not merge avi files. sorry

please read the official guide.
http://www.dvdfab.com/docs/

sory i rong file i use convertxtodvd then try to merge 1 dvd that was split into 2 avi and convert them to dvd and then try to merge in dvdfab and it stops responding and then closes on its own can you or any one help thanks

had a copy of dvdfab 3.??? one day i was trying to merge a movie that was split into 2 parts when i start the mergeing it just stop and was not responding so i got the upgrade 5.??? and it does the same thing
i have uninstalld it and reinstalld it same thing can any one help