Problem with DOS app on Windows 2000

I have a windows peer to peer network set up 7 being Windows 98 8th one being Windows 2000 Pro where the database sits. So the application being DOS can be used on all machines which has no problem. But I have a problem with the Windows 2000 machinewhere when using the application as well as the rest of them using it,it kicks itself to the taskbar every 5 mins then you have to keep restoring the program from the taskbar or pressing enter to bring it to full screen again and it only happens on the Windows 2000 machines. Powermanagement is turned off, config.nt has files=101, registry entry useopportunisticlocking dword is added. But why it is minimising itself even when using the dos application I’m lost any suggestion ?