We use a DOS program that moves data between the PC and hand-held computers. This app is pre-1990. I'm assuming since this app is quite OLD, that it must install a TSR and use DOS interrupts from the serial port UARTS.

This seems runs on all 9x (including ME from August 2000 update) & NT platforms. But I don't know why it runs on ME, NT 4.0 & Win2000. I am under the impression that the newer platforms restrict access to the hardware even more than in pre-Win98SE version.

Can someone explain how, why and for how much longer we can depend upon the program?