change com port

hi, I am a Digi One SP virgin. I installed a SP on a test PC and it allocated Com 3 to the SP. I tested the software on the test PC to make sure I had the SP set up correctly and that everything would work. It did. I then installed the SP and another one onto our live PC and they were allocated com 4 and 5. How can I change the com 5 SP to point to Com 3?

sorry left out that I am using windows XP professional

You should be able to renumber the ports via Device Manager.