windows 95 application running on windows xp problems

i purchased 6 new pc’s and changed from windows 98 to windows xp. i run a database program that was for win 95/98. the database is one one win xp pc and the other 5 pc’s just map the that pc’s drive. the trouble i have is the when more than 2 pc login and access the application and move around the app. it is really slow and when they close the program it take for ever to close. what do i need to look at to make this work. also i moved the old win 98 pc with the database on it and replaced it with the mew xp pc with the database and all the new xp pc’s work great.