Connect 2 Win 7 PCs via RS-232 DB9 serial cable

You have to use a terminal program like putty or something similar to communicate over the serial port. Windows supports the ports but doesn't include Hyperterminal in Win 7. So you need to get something that works like Hyperterminal.

You also need a cross-over cable. I'm assuming the link in the first comment noted that but in case it didn't... A cross-over will cross pins 2 & 3 as well as the handshaking pins.

Finally, all serial ports show up as COM ports in Windows. Even if it is a USB to serial port adapter or a Bluetooth to serial port (support the SPP profile). So the device driver for the specific adapter must implement a virtual COM port. Your terminal app will simply need to know the COM port number.

Serial connections are dumb connections. Device manager doesn't monitor the state of the serial connection. It isn't like a network link where Windows will tell you if a cable is unplugged. There is no supervisor function on a serial port. So if the hardware is there and the driver loaded, it will show in device manager regardless of whether something is actually hooked to it or not. You will never see any kind of state indicator in Device Manager.

You can, in fact, send things to a serial port that isn't connected to anything at all. Your terminal program will be perfectly happy doing that. State management and error detection are the domain of the application using the port. It is very different than a regular network connection.

When you say that data is not exchanged, what exactly do you mean? How are you trying to exchange data? Are you opening the terminal program on both machines, setting them to the same baud and port settings, then getting nothing on the other machine when you type into the first? If this is the case, make sure you are setting both sides to no flow control. Depending on the cable, it may not be properly passing the hardware handshakes between the machines. If the port is setup to use hardware flow control (the default setting), it will not pass data until it sees the CTS signal from the other side. Configuring the port to no flow control will make it ignore all of that and send the data regardless of the status of the other side.