Windows 7: Cannot change dial up network bps and flow control on com1

A dial up network can be created using a direct connect cable between two pc by using the following procedures:

1. create a direct connect modem first:
control panel->hardware->device manager->modem->action->add legacy->next->manual select from list->next->modems->next->don't detect->next->comm cable between two pc->next->com1->next->finish

2. create a dial up network:
control panel->network->view network status->setup new connection->setup dial up connection->next->comm cable between two pc->next->enter user name and password->connect->skip->close

3. Cannot change bps and flow control
control panel->network->connect to a network->right click on the dialup network just created-> properties-> configure->change the bps 38400 and no hardware flow control->ok->ok->

connect to a network->right click on the dialup network just created-> properties-> configure->bps is still 19200 and hardware flow control is still enabled.

This problem only exists on com1.

Your help is appreciated.