I have installed hvacpro on two computers that have xp running. The first is a dell using a usb to com port adapter and the other is a winbook that has a com port. Both computers I can use the com port for gx9100 and other programs but when I try to connect to a device through hvacpro with a cablepro I get an error that says com port in use by a dos application, then it will say do you want to reassign, it you say yes it cycles the same screens again. Is this a common problem how do I fix this. thanks in advance.