Dos and Windows don't always get along. I understand that Easyroute is supposed to be good, but we use Quick Books Pro. I will not load anything that isn't a 32 bit application on to this PC. You're asking for trouble..... If the programmer developed a 32bit product, I'll look them, but anything past Win 98 would be a risk in my opinion.
Quick Books Pro can also be set up for service companies, and you would do this as you set the program up.
Beth