Virtual Serial Ports Driver for Windows XP (VSPD XP) creates two pure virtual serial ports in your system which are virtually connected to each other.

For other Windows applications, virtual ports will be seen exactly as two real serial ports connected via null-modem cable. You can select any port numbers for virtual pair. For example, you can create virtual pair COM5-COM6. In this case all data sent by other applications to COM5 will arrive at COM6, and all data sent to COM6 will arrive at COM5. This can be seen if you run two HyperTerminals (or any other Windows terminal programs) and connect one of them to COM5 and other one to COM6. Then, all you type in first terminal will appear at second one. Of course, you can transfer files, other data or do whatever you want as it was real serial ports. With VSPD XP you can connect one application to another using virtual serial ports pair. Applications will be able to exchange data. This solution can be used, for example, for GPS simulation programs.
Full features list:

You can control virtual serial ports directly from your own application new

"Hot" installation - no reboot required either for installation or for creation of virtual serial ports

You can create as many virtual serial ports pairs as you want

Virtual Serial Ports are absolutely the same copies of real one - other applications will never see the difference between real serial port and virtual serial port

Real serial ports are not occupied

You even can have no real serial ports in your system
Link between virtual serial ports is much faster then real null-modem cable connection and depends on your processor speed
Average transfer speed is about 35-40 Kbytes/sec
 VSPD XP uses advanced Windows NT kernel driver technology (supporting WDM, WMI, Power Management, PNP, etc.)

Virtual Link is much more reliable than common physical link

With user friendly GUI and on-the-fly help it is very easy to configure virtual serial ports pair

Download Virtual Serial Ports Driver XP 4.0